Revert "[Profile picker] Reenable a previously flaky test"

This reverts commit c40e539d.

Reason for revert: The test is still flaky (with another failure).

Original change's description:
> [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}

TBR=droger@chromium.org,jkrcal@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1144065
Change-Id: If28415db9dbebed1b9eb2ea80df49ad80bd7887b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2571698Reviewed-by: Jan Krcal <jkrcal@chromium.org>
Commit-Queue: Jan Krcal <jkrcal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833423}

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

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