s/Get(Master|Replica)X/Get\1/g (#29520)

Drop the legacy `X` suffix from `GetMasterX` and `GetReplicaX`. The
presence of the suffix suggests there's a `non-X` version: but in fact
we migrated these away a long time ago, so remove the cognitive
overhead.

As an aside, this additionally helps avoid trip up LLMs that interpret
this as "something to fix".

server/channels/store/sqlstore/integrity.go

@@ -57,7 +57,7 @@ func getOrphanedRecords(ss *SqlStore, cfg relationalCheckConfig) ([]model.Orphan
 		return nil, err
 	}
 
-	err = ss.GetMasterX().Select(&records, query, args...)
+	err = ss.GetMaster().Select(&records, query, args...)
 	return records, err
 }