Disable flaky tests within weblayer_private_instrumentation_test_apk

Bug: 1223953
Change-Id: Ia2aa6e2676e207b37d634cf06f7283e884730645
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3114987


Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/main@{#914515}