Enable FF "tags_finder_gitaly" by default

What does this MR do and why?

• Contributes to #339741 (closed)
• Original MR: !69101 (merged)

FF was globally enabled and seems stable enough to use it for self hosted instances.

It is going to enable Gitaly based sorting for tags by default.

Upd

I discovered that gitaly_ is a reserved name for Gitaly specific features. I've renamed gitaly_tags_finder -> tags_finder_gitaly. This change should not affect production because the renamed feature flag is enabled by default.

Screenshots or screen recordings

See !69101 (merged)

How to set up and validate locally

See !69101 (merged)

MR acceptance checklist

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