Following SERVER-99433's removal of the RS endpoint logic, the shouldUpdateClusterCardinality removeShard coordinator parameter became redundant as it's never supposed to be true (if a cluster ever had more than 2 shards, the cluster cardinality will never be reset, even when only 1 shard remains).

Purpose of this ticket is to get rid of it once 9.0 branches out (before that, it is needed for backwards compatibility). This should be safe because the bool field was required until v8.2 and was switched to optionalBool in v8.3,it follows that it will be optional in v9.0 and safely removable in v9.1.