[Gardener] Disable flaky UserScriptsAPITests on CrOS MSan

Disable UserScriptsAPITest.RegisterUserScripts and
UserScriptsAPITest.ConfigureWorld, as they are flaky on Linux ChromiumOS
MSan Tests.

Bug: 335421977
Change-Id: I927cb8214a5a00a8ac4b83b8b3b22297968eda0b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5463213


Owners-Override: Andy Phan <andyphan@chromium.org>
Commit-Queue: Nina Satragno <nsatragno@chromium.org>
Reviewed-by: Nina Satragno <nsatragno@chromium.org>
Auto-Submit: Andy Phan <andyphan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1289601}