Remove feature flag optimize_container_repository_has_tags

What does this MR do and why?

This MR remove the feature flag optimize_container_repository_has_tags and fully releases the optimization that we did to ContainerRepository#has_tags?.

Rolled out 100% in production: https://gitlab.slack.com/archives/C101F3796/p1753986636564149

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Related to #556772 (closed)