Enable deployments filters

What does this MR do?

This removes the deployment_filters feature flag and permanently enables the gated behaviour for all users.

• Rollout issue: #267561 (closed)
• Documentation MR: !46343 (merged)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content