Remove long-dead comments.

These should've been dropped by a8bb8eb5, but evidently were
missed.  Not important enough to back-patch.

src/backend/commands/user.c

@@ -1445,8 +1445,6 @@ roleSpecsToIds(List *memberNames)
  * memberIds: OIDs of roles to add
  * grantorId: who is granting the membership
  * admin_opt: granting admin option?
- *
- * Note: caller is responsible for calling auth_file_update_needed().
  */
 static void
 AddRoleMems(const char *rolename, Oid roleid,
@@ -1589,8 +1587,6 @@ AddRoleMems(const char *rolename, Oid roleid,
  * memberSpecs: list of RoleSpec of roles to del (used only for error messages)
  * memberIds: OIDs of roles to del
  * admin_opt: remove admin option only?
- *
- * Note: caller is responsible for calling auth_file_update_needed().
  */
 static void
 DelRoleMems(const char *rolename, Oid roleid,