Disable glic window position tests on Linux

On some headless Linux environments, the virtual screen size is 0x0
which causes the glic widget position to be clamped.

This doesn't reflect any real use case so I believe it's better to
disable those tests on Linux rather than change the test expectations.
Window position should work similarly enough on the other platforms
that we aren't losing much by disabling the tests.

Bug: b:416094068
Change-Id: I29849a396792ace3fd50a5349867ee081d837bdd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6577144
Auto-Submit: Ian Wells <iwells@chromium.org>
Commit-Queue: Ian Wells <iwells@chromium.org>
Reviewed-by: Carlos Knippschild <carlosk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1464304}