Revert "[ozone/x11] Enabled user input monitor unit tests."

This reverts commit 30a60064ee373b6b97c923c16063144ef0ca505f.

Reason for revert: Suspicious about causing test failures.
https://ci.chromium.org/p/chromium/builders/ci/linux-lacros-tester-rel/4433

Original change's description:
> [ozone/x11] Enabled user input monitor unit tests.
>
> This CL adds Ozone platform initialisation to the user input monitor tests
> so they can now work with Ozone enabled.
>
> Bug: 1109112
> Change-Id: I31f9dabf2da9eed85cd05fe27017899b0247f4bc
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2521144
> Commit-Queue: Alexander Dunaev <adunaev@igalia.com>
> Reviewed-by: Scott Violet <sky@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#826638}

TBR=sky@chromium.org,adunaev@igalia.com

Change-Id: Ic8cd3da17dd5d2de01981aa9a8f33b6a55621c43
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1109112
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2531810
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826688}