Disable CredentialsContainerTest.PendingGetRequest_NoGCCycles test.

This was failing due to "unified garbage collection",
https://chromium-review.googlesource.com/c/chromium/src/+/1290869.

TBR=mlippautz@chromium.org, haraken@chromium.org, mkwst@chromium.org, vasilii@chromium.org

NOTRY=True

Bug: 902286
Change-Id: Ia5a8fd654f668d7b13d19fb44d39bd80809f9807
Reviewed-on: https://chromium-review.googlesource.com/c/1319672Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605662}

third_party/blink/renderer/modules/credentialmanager/credentials_container_test.cc

@@ -120,7 +120,9 @@ class CredentialManagerTestingContext {
 // The completion callbacks for pending mojom::CredentialManager calls each own
 // a persistent handle to a ScriptPromiseResolver instance. Ensure that if the
 // document is destored while a call is pending, it can still be freed up.
-TEST(CredentialsContainerTest, PendingGetRequest_NoGCCycles) {
+// TODO(https://crbug.com/902286): This test was disabled due to failures caused
+// by "unified garbage collections", fix the test and re-enable it.
+TEST(CredentialsContainerTest, DISABLED_PendingGetRequest_NoGCCycles) {
   MockCredentialManager mock_credential_manager;
   GCObjectLivenessObserver<Document> document_observer;