[icu] Disables a `PartitionAllocTest` that seems flaky on ChromeOS

The `PartitionAllocTest.CheckReservationType` started to fail
on Fuchsia when upgrading ICU to 74, and fails on ChromeOS
when upgrading ICU to 77.1[1].

This patch disables the test on ChromeOS to unblock the
ICU upgrade.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/6578333/24?checksRunsSelected=linux-chromeos-rel&tab=checks

Bug: 331366007, 421834885
Change-Id: I5ded47e3b4ed55f11f26428e64540dc528b3f4d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6942450
Reviewed-by: Takashi Sakamoto <tasak@google.com>
Auto-Submit: Koji Ishii <kojii@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1514682}