Remove useless casts to (void *)

Many of them just seem to have been copied around for no real reason.
Their presence causes (small) risks of hiding actual type mismatches
or silently discarding qualifiers

Discussion: https://www.postgresql.org/message-id/flat/461ea37c-8b58-43b4-9736-52884e862820@eisentraut.org

src/backend/rewrite/rewriteDefine.c

@@ -644,7 +644,7 @@ setRuleCheckAsUser_walker(Node *node, Oid *context)
 		return false;
 	}
 	return expression_tree_walker(node, setRuleCheckAsUser_walker,
-								  (void *) context);
+								  context);
 }
 
 static void
@@ -679,7 +679,7 @@ setRuleCheckAsUser_Query(Query *qry, Oid userid)
 
 	/* If there are sublinks, search for them and process their RTEs */
 	if (qry->hasSubLinks)
-		query_tree_walker(qry, setRuleCheckAsUser_walker, (void *) &userid,
+		query_tree_walker(qry, setRuleCheckAsUser_walker, &userid,
 						  QTW_IGNORE_RC_SUBQUERIES);
 }