Remove `inline_project_authorizations_refresh_only_for_single_element` feature flag.

What does this MR do and why?

Removing the flag inline_project_authorizations_refresh_only_for_single_element introduced in !91572 (merged).

It is fully enabled on production now, and is working as expected, so this flag can be safely removed.

Rollout issue is #366815 (closed)

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