Resolve "[Feature flag] Rollout of `usage_data_ci_i_testing_coverage_report_uploaded`"

What does this MR do and why?

Related !102371 (merged)

The purpose of this MR is to remove the feature flag for the artifacts reports - coverage_report.

As there have been no issues so far, feature flag can now be removed.

All Artifacts reports cobertura (coverage_report) uploads are available behind the metric feature flag usage_data_ci_i_testing_coverage_report_uploaded

• Remove usage_data_ci_i_testing_coverage_report_uploaded feature flag

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #383793 (closed)