Revert "fix: restore old behaviour of empty json w/ 401 code in admin middleware" [breaking]

This reverts commit dda5d42610.

re: #11099

src/middleware/admin.js

@@ -81,7 +81,7 @@ middleware.checkPrivileges = helpers.try(async (req, res, next) => {
 	}
 
 	if (res.locals.isAPI) {
-		res.status(401).json({});
+		controllers.helpers.formatApiResponse(401, res);
 	} else {
 		res.redirect(`${nconf.get('relative_path')}/login?local=1`);
 	}