Remove HDMI plug-off subtest

Remove this subtest on factory branch since plug-off is not supported yet.
Revert this CL once we have plug-off supported.

BUG=chrome-os-partner:9879
TEST=run factory_ExtDisplay on snow dvt board, can pass the plug-on
subtest. And the test is passed.

Change-Id: I46d38c9489facb2d192662dfbb1ffb8e6b07b113
Reviewed-on: https://gerrit.chromium.org/gerrit/27140
Reviewed-by: Chinyue Chen <chinyue@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
1 file changed