Fix a memory leak in disableNoticeReporting

de0aff5 turned a potentially large memory leak
that might not be a leak at all into a guaranteed small leak whenever
you call disableNoiceReporting on a connection that was in the
enableNoticeReporting state.

cbits/noticehandlers.c

@@ -56,4 +56,5 @@ hs_postgresql_libpq_free_noticebuffer (NoticeBuffer * arg) {
     free(x);
     x = nx;
   }
+  free(arg);
 }