submodule--helper: don't redundantly check "else if (res)"

The "res" variable must be true at this point in update_submodule(),
as just a few lines above this we've unconditionally:

	if (!res)
		return 0;

So we don't need to guard the "return 1" with an "else if (res)", we
can return unconditionally at this point. See b3c5f5cb04 (submodule:
move core cmd_update() logic to C, 2022-03-15) for the initial
introduction of this code, this check of "res" has always been
redundant.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Reviewed-by: Glen Choo <chooglen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/submodule--helper.c

@@ -2445,8 +2445,7 @@ static int update_submodule(struct update_data *update_data)
 			    update_data->displaypath);
 		if (res == 128)
 			exit(res);
-		else if (res)
+		return 1;
-			return 1;
 	}
 
 	return 0;