Limit all Sentry responses for Error Tracking

What does this MR do and why?

This MR enables the limit of 1 megabytes for all Sentry responses used for Error Tracking.

It removes feature flag error_tracking_sentry_limit added back in !84209 (merged).

See Rollout issue.

Screenshots or screen recordings

Within Limit	Limit exceeded	Limit exceeded during setup

How to set up and validate locally

1. Setup Sentry Integration with https://sentry.gitlab.net
2. Make sure feature flag is deleted via Feature.remove(:error_tracking_sentry_limit)
3. List errors and view details ✅
4. Tweak RESPONSE_SIZE_LIMIT to 1.kilobyte
5. List errors and see the error message showing up ✅

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.