[Sheriff] Disable two flaky SafeBrowsingBrowserTest tests

Disable consistently failing tests:
- NoAccessTokenFetchInRealTimeUrlLookupsUnlessEnabled
- UnfulfilledAccessTokenFetchTimesOutAndNavigationCompletes

Bug: 1448377
Change-Id: I9504ed7116705fec63c2a444c03c459a4454d8de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4558766


Owners-Override: Aishwarya Rajesh <aishwaryarj@google.com>
Reviewed-by: Shu Yang <shuyng@google.com>
Commit-Queue: Aishwarya Rajesh <aishwaryarj@google.com>
Cr-Commit-Position: refs/heads/main@{#1148280}