Part of the optimisations proposed by SERVER-56786 implied the creation of a new version of the config server command to mergeChunks, while also keeping the old one to ensure interoperability between nodes running different versions of MDB.

Now that v5.0 (which includes the changes introduced by SERVER-56786) has been released, the support to the legacy version of the command is no longer needed and the code can be cleaned up: more specifically, it is possible to remove

• the function in charge of invoking the legacy CS command from the shard

• The definition and boilerplate code of the CS command

• The logic behind the command

• The unit test of the command