Remove the `pipeline_execution_schedule_policy` experiment flag and related experiment checks now that the scheduled pipeline execution policies feature has been fully rolled out. ## Why The `scheduled_pipeline_execution_policies` feature flag was removed in !212227, but the feature is still gated behind the `pipeline_execution_schedule_policy` experiment flag. Since we're moving toward GA release, we should remove the experiment flag to fully enable the feature. ## Implementation - [ ] Remove experiment flag checks from backend code - [ ] Remove experiment flag checks from frontend code - [ ] Update tests to remove experiment-related test cases - [ ] Update documentation if needed ## Related - Epic: &17875 (GA release epic) - MR: !212227 (removed feature flag)