Making testAllAppsFromHome platinum

This test has a search for Youtube, which makes it possible for this test to replace android.platform.test.scenario.launcher.integration_tests.ScrollDownToSearchYoutubeFromAllApps#scrollDownToYouTube

Removing ScrollDownToSearchYoutubeFromAllApps#scrollDownToYouTube would move close to a state where the only Platinum tests outside of Launcher projects are ones that use 1P apps. This will make it easier to divide responsibilities between the IW and the Launcher teams.

Test: presubmit
Flag: N/A
Bug: 187761685
Change-Id: I889b1b23e5fe0a543eba24a922dc6908ac887305

tests/src/com/android/launcher3/allapps/TaplOpenCloseAllAppsTest.java

@@ -130,6 +130,7 @@ public class TaplOpenCloseAllAppsTest extends AbstractLauncherUiTest {
      */
     @Test
     @PortraitLandscape
+    @PlatinumTest(focusArea = "launcher")
     public void testAllAppsFromHome() {
         // Test opening all apps
         assertNotNull("switchToAllApps() returned null",