Update ENV Vars for AI Gateway Component

What does this MR do and why?

Relates to https://gitlab.com/gitlab-org/quality/quality-engineering/team-tasks/-/issues/2128 and https://gitlab.com/gitlab-org/quality/quality-engineering/team-tasks/-/issues/2262

This MR:

• Updates the environment variables passed to the AI gateway component to match the new required format (see example.env for details)
• Removes the USE_LOCAL_CACHE environment variable as it is no longer in use
• Removes the QA_USE_SYNC_SERVICE_TOKEN_WORKER environment variable and its references to stick with using the default state of <code data-sourcepos="15:133-15:161">use_sync_service_token_worker</code> instead, so that this helps simplify setup for future scenarios (please also see this discussion around keeping vs. removing it)

Test pipeline showing dequarantined spec in gitlab!141519 (merged) now passes as expected: https://gitlab.com/gitlab-org/gitlab-qa/-/jobs/5911922744

MR acceptance checklist

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