Set repository_set_cache_logging feature flag to default enabled

What does this MR do and why?

This MR default enables the feature flag repository_set_cache_logging. To do this I have have changed the type from gitlab_com_derisk to beta

The flag is 100% enabled on Gitlab.com

References

• Rollout Issue: [Feature flag] Rollout of `repository_set_cache... (#549485 - closed)
• Logging Issue: Add logging to understand impact of SetReposito... (#517676 - closed)
• Bug: Gitlab::RepositorySetCache#fetch is not atomic (#506430)

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Related to #549485 (closed)