tests: disable plugin_hint test
tests: disable plugin_hint test

This test uses kill(getppid(), SIGSTOP), which stops the cargo test
runner process instead of crosvm as intended.

Skip it until someone has time to fix it.

BUG=b:239094055
TEST=cargo test --features=plugin -- --test-threads=1

Change-Id: Ib41351154bc585cecc8471f0150f393ce9431da9
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3764464
Reviewed-by: Dennis Kempin <cd09796fb571bec2782819dbfd33307f65b1c778@google.com>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Tested-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm