After backporting SERVER-71479 to v6.0 (BACKPORT-14282) we may have a scenario where the shard is not including the `validAfter` field on `_configsvrCommitChunksMerge` command, while the config server expects it. In that case command fails with error message "chunk operation requires validAfter timestamp"

This happens only when config server has a version that doesn't include the SERVER-71479 feature while shard does. Since the config server is upgraded before shards on a cluster upgrade, this was not needed on master. It is needed on backporting tickets though because, for instance, we can upgrade from v6.0 (which has the feature SERVER-71479) to v6.1 (which doesn't).