As part of this ticket, we should:
1. Remove featureFlagViewlessTimeseriesUpgradeDowngradeRetriableError
2. Update this conditional statement to rely on gFeatureFlagCreateViewlessTimeseriesCollections.isEnabledAndIgnoreFCVUnsafe() instead of gFeatureFlagViewlessTimeseriesUpgradeDowngradeRetriableError.isEnabled()
3. Fix the relevant unit tests in shard_role_test.cpp, i.e., RestoreForReadFailsOnTimeseriesCollectionDowngradeThroughMainNss, RestoreForRightFailsOnTimeseriesCollectionDowngradeThroughMainNss, RestoreForReadFailsOnTimeseriesCollectionDowngradeThroughBucketsNss, and RestoreForRightFailsOnTimeseriesCollectionDowngradeThroughBucketsNss.