test: Readable order for ad test setup (#5468)

For readability, the order of before*/after* functions should be the
same as their execution order:
 - beforeAll
 - beforeEach
 - afterEach
 - afterAll

This fixes the order for ad tests.

test/ui/ad_ui_unit.js

@@ -25,15 +25,6 @@ describe('Ad UI', () => {
     shaka.Player.setAdManagerFactory(() => new shaka.test.FakeAdManager());
   });
 
-  afterEach(async () => {
-    await UiUtils.cleanupUI();
-  });
-
-  afterAll(() => {
-    document.head.removeChild(cssLink);
-    shaka.Player.setAdManagerFactory(() => new shaka.ads.AdManager());
-  });
-
   beforeEach(() => {
     container =
       /** @type {!HTMLElement} */ (document.createElement('div'));
@@ -45,6 +36,15 @@ describe('Ad UI', () => {
     adManager = video['ui'].getControls().getPlayer().getAdManager();
   });
 
+  afterEach(async () => {
+    await UiUtils.cleanupUI();
+  });
+
+  afterAll(() => {
+    document.head.removeChild(cssLink);
+    shaka.Player.setAdManagerFactory(() => new shaka.ads.AdManager());
+  });
+
   it('is invisible if no ad is playing', () => {
     const adControlsContainer =
         UiUtils.getElementByClassName(container, 'shaka-ad-controls');