Now that mongoD applies the default read/write concern, we should be able to remove the majority write concern override in the replica_sets_transition_to_csrs_jscore_passthrough suite. Doing so will also increase our coverage of this application of defaults on the mongoDs.

However, I think we still need the overwrite of majority since we are running with stepdowns for read concern and currently the overwrite read/write concern hook does not allow applying only the read concern.