[Sheriff] Disable MachineLearningServiceBrowserTest.LaunchAndTerminate

The test is flaky on multiple platforms.

TBR=jiakl@google.com,mcrouse@chromium.org

Bug: 1122160
Change-Id: I0d6a7354fc5969a9e01efefb17c7c6fd1c67b018
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2378396Reviewed-by: Michael Crouse <mcrouse@chromium.org>
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801968}

chrome/browser/optimization_guide/prediction/machine_learning_service_browsertest.cc

@@ -93,7 +93,8 @@ void RetryForHistogramUntilCountReached(base::HistogramTester* histogram_tester,
 
 using MachineLearningServiceBrowserTest = InProcessBrowserTest;
 
-IN_PROC_BROWSER_TEST_F(MachineLearningServiceBrowserTest, LaunchAndTerminate) {
+// The test is flaky: crbug.com/1122160
+IN_PROC_BROWSER_TEST_F(MachineLearningServiceBrowserTest, DISABLED_LaunchAndTerminate) {
   base::HistogramTester histogram_tester;
   ServiceProcessObserver observer;
   auto* service_connection = ServiceConnection::GetInstance();