Bug report: custom feedback button survey does not obey positioning customisation

[danazou]

Bug Description

Created a survey based on a custom feedback button and customised the positioning to be "Center". However, in practice, the survey is sticking to the left. More information (including call recording with screenshots) in this Slack message

Additional context

The feedback button is implemented in a VSCode plugin. The feedback button is not in the plugin page, instead it is on top of the plugin page – i.e. there is no physical button on the page where a class name can be added to PostHog. So the customer created an invisible button that gets 'clicked on' when user generates "feedback button clicked" event.

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables or https://eu.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]