Remove optimized_codeowners_pattern_matching feature flag

Vasilii Iakliushinrequested to merge
601529-remove-optimized-codeowners-pattern-matching-ff into master

What does this MR do and why?

Contributes to #601529 (closed)

Problem

The optimized Code Owners path is ready to stay enabled, but its rollout feature flag and fallback matcher are no longer needed.

Solution

  • Keep PatternIndex as the only path matching implementation.
  • Remove the dead brute-force matcher and path_matches? helper.
  • Collapse the flag-specific examples into one shared spec context.
  • Delete the feature flag definition for optimized pattern matching.

References

Merge request reports