fix test

Author: SimenB

e2e/fake-promises/immediate/__tests__/generator.test.js

@@ -13,6 +13,7 @@ test('fake promises', () => {
     someValue = 'foobar';
   });
 
+  // this function is only available when using legacy fake timers
   jest.runAllImmediates();
 
   expect(someValue).toBe('foobar');

e2e/fake-promises/immediate/package.json

@@ -1,6 +1,6 @@
 {
   "jest": {
-    "timers": "fake",
+    "timers": "legacy",
     "setupFiles": [
       "<rootDir>/fake-promises"
     ],