amcheck: Fix code comments

Code comments were claiming that verify_heapam() was checking
privileges on the relation it was operating on, but it didn't actually
do that.  Perhaps earlier versions of the patch did that, but now the
access is regulated by privileges on the function.  Remove the wrong
comments.

contrib/amcheck/verify_heapam.c

@@ -298,7 +298,7 @@ verify_heapam(PG_FUNCTION_ARGS)
 	rsinfo->setDesc = ctx.tupdesc;
 	MemoryContextSwitchTo(old_context);
 
-	/* Open relation, check relkind and access method, and check privileges */
+	/* Open relation, check relkind and access method */
 	ctx.rel = relation_open(relid, AccessShareLock);
 	sanity_check_relation(ctx.rel);
 
@@ -524,8 +524,7 @@ verify_heapam(PG_FUNCTION_ARGS)
 }
 
 /*
- * Check that a relation's relkind and access method are both supported,
- * and that the caller has select privilege on the relation.
+ * Check that a relation's relkind and access method are both supported.
  */
 static void
 sanity_check_relation(Relation rel)