Remove outdated comment and clarify code

The comment about backporting to a 10 year old version has passed
it's due date so remove. Also actually use the referenced variable
to make the code less confusing to readers (the compiler will be
smart enough about stack allocations anyways). Also reflows and
generally tidies up the comment a little.

src/backend/utils/adt/ruleutils.c

@@ -7903,15 +7903,16 @@ pg_get_partition_def_ext(PG_FUNCTION_ARGS)
 	bool		pretty = PG_GETARG_BOOL(1);
 	int			prettyFlags;
 	char	   *str;
+	bool		bLeafTablename = FALSE;
 
 	prettyFlags = pretty ? PRETTYFLAG_PAREN | PRETTYFLAG_INDENT : 0;
 
-	/* MPP-6297: don't dump by tablename here 
-	 * NOTE: may need to backport fix to 3.3.x, and changing
-	 * bLeafTablename = TRUE here should only affect
-	 * pg_dump/cdb_dump_agent (and partition.sql test) 
+	/*
+	 * MPP-6297: don't dump by tablename here. NOTE: changing bLeafTablename to
+	 * TRUE here should only affect pg_dump/cdb_dump_agent (and partition.sql
+	 * test)
 	 */ 
-	str = pg_get_partition_def_worker(relid, prettyFlags, FALSE); 
+	str = pg_get_partition_def_worker(relid, prettyFlags, bLeafTablename);
 	
 	if (!str)
 		PG_RETURN_NULL();