pg_upgrade: Make format strings consistent

The backport of commit f295494d33 introduced a format string using
%m.  This is not wrong, since those have been supported since commit
d6c55de1f9, but only commit 2c8118ee5d later introduced their use
in this file.  This use introduces a gratuitously different
translatable string and also makes it inconsistent with the rest of
the file.  To avoid that, switch this back to the old-style strerror()
route in the appropriate backbranches

src/bin/pg_upgrade/check.c

@@ -1282,7 +1282,7 @@ check_for_not_null_inheritance(ClusterInfo *cluster)
 		for (int i = 0; i < ntup; i++)
 		{
 			if (script == NULL && (script = fopen_priv(output_path, "w")) == NULL)
-				pg_fatal("could not open file \"%s\": %m", output_path);
+				pg_fatal("could not open file \"%s\": %s", output_path, strerror(errno));
 			if (!db_used)
 			{
 				fprintf(script, "In database: %s\n", active_db->db_name);