Disable flaky test: testManualGenerationCancel

Similar to https://chromium-review.googlesource.com/c/chromium/src/+/1836031
this patch disables another very flaky test causing failures
on the bots.

Example bot:
https://ci.chromium.org/p/chromium/builders/ci/android-marshmallow-arm64-rel/17969

Flakes:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=chrome_public_test_apk&tests=PasswordGenerationIntegrationTest

TBR: vasilii@chromium.org, fhorschig@chromium.org
Bug: 1010540
Change-Id: I684f794a971dc1b44a98e54184c8b0b475578d6a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1835167Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702188}

chrome/android/features/keyboard_accessory/javatests/src/org/chromium/chrome/browser/keyboard_accessory/PasswordGenerationIntegrationTest.java

@@ -94,6 +94,7 @@ public class PasswordGenerationIntegrationTest {
 
     @Test
     @IntegrationTest
+    @DisabledTest(message = "crbug.com/1010540")
     public void testManualGenerationCancel() throws InterruptedException, TimeoutException {
         waitForGenerationLabel();
         focusField(PASSWORD_NODE_ID_MANUAL);