Remove unneeded volatile qualifier in fmgr.c.

Currently, the save_nestlevel variable in fmgr_security_definer()
is marked volatile.  While this may have been necessary when it was
used in a PG_CATCH section (as explained in the comment for PG_TRY
in elog.h), it appears to have been unnecessary since commit
82a4798, which removed its use in a PG_CATCH section.

Author: Julien Rouhaud <[email protected]>
Reviewed-by: Bertrand Drouvot <[email protected]>
Discussion: https://postgr.es/m/Z6xbAgXKY2L-3d5Q%40jrouhaud

Author: nathan-bossart

src/backend/utils/fmgr/fmgr.c

@@ -639,7 +639,7 @@ fmgr_security_definer(PG_FUNCTION_ARGS)
 	ListCell   *lc1,
 			   *lc2,
 			   *lc3;
-	volatile int save_nestlevel;
+	int			save_nestlevel;
 	PgStat_FunctionCallUsage fcusage;
 
 	if (!fcinfo->flinfo->fn_extra)