Revert unnecessary change in MV call to checkRuleResultList().

Due to a misreading of the function's comment block, there was an
unneeded change to a call in rewriteDefine.c.  There is, in fact
no reason to pass false for a MV; it should be true just like a
view.

Fixes issue pointed out by Tom Lane

src/backend/rewrite/rewriteDefine.c

@@ -356,8 +356,7 @@ DefineQueryRewrite(char *rulename,
 		 */
 		checkRuleResultList(query->targetList,
 							RelationGetDescr(event_relation),
-							event_relation->rd_rel->relkind !=
-								RELKIND_MATVIEW);
+							true);
 
 		/*
 		 * ... there must not be another ON SELECT rule already ...