change tests to 'use client'

Author: zth

jscomp/test/directives.js

@@ -1,5 +1,5 @@
-first directive;
-second directive;
+"use client";
+'use client';
 'use strict';
 
 var Belt_Array = require("../../lib/js/belt_Array.js");

jscomp/test/directives.res

@@ -1,5 +1,5 @@
-@@directive("first directive;")
-@@directive("second directive;")
+@@directive(`"use client";`)
+@@directive("'use client';")
 
 let a = Belt.Array.forEach