[Profile picker] Reenable a previously flaky test

This CL reenables the CreateSignedInProfileSigninAlreadyExists test
within the ProfilePickerCreationFlowBrowserTest suite. The underlying
bug has been fixed by a previous CL.

Bug: 1144065
Change-Id: I7b15ff47f4eb8c3e16214269bc98a7f23bddbf01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2563671
Auto-Submit: Jan Krcal <jkrcal@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Jan Krcal <jkrcal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832273}

chrome/browser/ui/views/profiles/profile_picker_view_browsertest.cc

@@ -472,9 +472,8 @@ IN_PROC_BROWSER_TEST_F(ProfilePickerCreationFlowBrowserTest,
                     kURL);
 }
 
-// TODO(crbug.com/1144065): Flaky on multiple platforms.
 IN_PROC_BROWSER_TEST_F(ProfilePickerCreationFlowBrowserTest,
-                       DISABLED_CreateSignedInProfileSigninAlreadyExists) {
+                       CreateSignedInProfileSigninAlreadyExists) {
   ASSERT_EQ(1u, BrowserList::GetInstance()->size());
 
   // Create a pre-existing profile syncing with the same account as the profile