docs: Remove old A/B testing doc (#8258)

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## About the changes
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Now that we are building out our Use Case tutorials to include A/B
testing, we can remove old content that is associated.

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website/docs/how-to/how-to-capture-impression-data.mdx

@@ -1,25 +1,26 @@
 ---
 title: How to capture impression data
 ---
-import ApiRequest from '@site/src/components/ApiRequest'
-import VideoContent from '@site/src/components/VideoContent.jsx'
+
+import ApiRequest from "@site/src/components/ApiRequest";
+import VideoContent from "@site/src/components/VideoContent.jsx";
 
 :::info Placeholders
 Placeholders in the code samples below are delimited by angle brackets (i.e. `<placeholder-name>`). You will need to replace them with the values that are correct in _your_ situation for the code samples to run properly.
 :::
 
-Unleash allows you to gather [**impression data**](../reference/impression-data.md) from your feature flags, giving you complete visibility into who checked what flags and when. What you do with this data is entirely up to you, but a common use case is to send it off to an aggregation and analytics service such as [Posthog](https://posthog.com/) or [Google Analytics](https://analytics.google.com/), either just for monitoring purposes or to facilitate [A/B testing](../topics/a-b-testing.md).
+Unleash allows you to gather [**impression data**](../reference/impression-data.md) from your feature flags, giving you complete visibility into who checked what flags and when. What you do with this data is entirely up to you, but a common use case is to send it off to an aggregation and analytics service such as [Posthog](https://posthog.com/) or [Google Analytics](https://analytics.google.com/), either just for monitoring purposes or to facilitate [A/B testing](../feature-flag-tutorials/use-cases/a-b-testing.md).
 
 This guide will take you through everything you need to do in Unleash to facilitate such a workflow. It will show you how to send data to Posthog as an example sink, but the exact same principles will apply to any other service of the same kind.
 
-<VideoContent videoUrls={["https://www.youtube.com/embed/bxYdeMb9ffw"]}/>
+<VideoContent videoUrls={["https://www.youtube.com/embed/bxYdeMb9ffw"]} />
 
 ## Prerequisites
 
 We will assume that you have the necessary details for your third-party service:
 
-- **where to send the data to**. We'll refer to this in the code samples below as **`<sink-url>`**.
-- **what format the data needs to be in**. This will determine how you transform the event data before you send it.
+-   **where to send the data to**. We'll refer to this in the code samples below as **`<sink-url>`**.
+-   **what format the data needs to be in**. This will determine how you transform the event data before you send it.
 
 In addition, you'll need to have a flag to record impression data for and an [Unleash client SDK](../reference/sdks/index.md) that supports impression data. This guide will use the [JavaScript proxy SDK](/docs/generated/sdks/client-side/javascript-browser.md).
 
@@ -37,7 +38,12 @@ When you create a new feature flag via the UI, there's an option at the end of t
 
 To create a feature flag with impression data enabled, set the `impressionData` option to `true` in the request payload, as seen below. For more options, check the [reference docs on creating features](/reference/api/legacy/unleash/admin/features-v2.md#create-toggle).
 
-<ApiRequest verb="post" payload={{name: "<feature-flag-name>", impressionData: true}} url="api/admin/projects/<project-id>/features" title="Create a feature flag with impression data enabled."/>
+<ApiRequest
+    verb="post"
+    payload={{ name: "<feature-flag-name>", impressionData: true }}
+    url="api/admin/projects/<project-id>/features"
+    title="Create a feature flag with impression data enabled."
+/>
 
 ### Enabling impression data for existing feature flags {#step-1-existing-toggles}
 
@@ -47,8 +53,12 @@ To enable impression data for an existing flag, go to the "Settings" tab of that
 
 To enable impression data for an existing flag, use the [API's flag patching functionality](/reference/api/legacy/unleash/admin/features-v2.md#patch-toggle):
 
-<ApiRequest verb="patch" payload={[{op: "replace", path: "/impressionData", value: true}]} url="api/admin/projects/<project-id>/features/<feature-flag-name>" title="Enable impression data on an existing flag."/>
-
+<ApiRequest
+    verb="patch"
+    payload={[{ op: "replace", path: "/impressionData", value: true }]}
+    url="api/admin/projects/<project-id>/features/<feature-flag-name>"
+    title="Enable impression data on an existing flag."
+/>
 
 ## Step 2: Capture impression events in your client {#step-2}
 
@@ -58,18 +68,17 @@ The steps below will use extracts from said documentation.
 
 After initializing the library, you'll probably also want to identify the current user, so that events can be correlated properly:
 
-``` js title="Identify the user."
+```js title="Identify the user."
 posthog.identify(userId);
 ```
 
 ### Capture and transform the event
 
 Attach an event listener to Unleash that listens for `"impression"` events. Inside the listener, transform the event data to the format you want and send it to your analytics service.
 
-``` js title="Capture, transform, and send impression data."
+```js title="Capture, transform, and send impression data."
 // listen for impression events
 unleash.on("impression", (event) => {
-
     // capture and transform events
     posthog.capture(event.eventType, {
         ...event.context,
@@ -78,7 +87,6 @@ unleash.on("impression", (event) => {
         enabled: event.enabled,
         variant: event.variant,
     });
-
 });
 ```