Remove replication slot name check from ReplicationSlotAcquire()

When trying to access a replication slot that is supposed to already
exist, we don't need to check the naming rules again.  If the slot
does not exist, we will then get a "does not exist" error message, which
is generally more useful from the perspective of an end user.

src/backend/replication/slot.c

@@ -331,8 +331,6 @@ ReplicationSlotAcquire(const char *name)
 
 	Assert(MyReplicationSlot == NULL);
 
-	ReplicationSlotValidateName(name, ERROR);
-
 	/* Search for the named slot and mark it active if we find it. */
 	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
 	for (i = 0; i < max_replication_slots; i++)