fix: Remove run all tests section (#12313)

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## **Description**

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also include relevant motivation and context. Have in mind the following
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1. What is the reason for the change?
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Run all test locally with a single command is not recommended as running
all tests are not ran in the same manner on CI. This will also prevent
some confusion with new contributors running all test the first time
which will take a long time. Removing the run all test section will make
it more clear to new contributors to run a specific test or a suite of
tests as currently documented and is more align with how we run test in
CI.
## **Related issues**

Fixes: team members running into issue attempting to run e2e test on
their local system for the first time.

## **Manual testing steps**

1. document running a single test
2. document running a suite of tests
3. no document for running all test with a single command

## **Screenshots/Recordings**

<!-- If applicable, add screenshots and/or recordings to visualize the
before and after of your change. -->

### **Before**

<!-- [screenshots/recordings] -->

### **After**

<!-- [screenshots/recordings] -->

## **Pre-merge author checklist**

- [ ] I’ve followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

docs/readme/testing.md

@@ -51,19 +51,6 @@ Ensure that these devices are set up. You can change the default devices at any
     yarn test:e2e:android:debug:build
     ```
 
-- **Run All Tests Locally**:
-  - **iOS Debug**:
-
-    ```bash
-    yarn test:e2e:ios:debug:run
-    ```
-
-  - **Android Debug**:
-
-    ```bash
-    yarn test:e2e:android:debug:run
-    ```
-
 - **Run Specific Tests**:
   - **iOS**: