Cleanup cache_control_headers_for_openid_jwks FF

Original issue: #374001 (closed)

Original MR: !138405 (merged)

Rollout issue: #433360 (closed)

What does this MR do and why?

Following rollout issue - #433360 (closed). As we didn't get any complains and by nature of the issue we can't reproduce it, we cleaning up enabled globally feature flag: cache_control_headers_for_openid_jwks

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