Remove --force-compositing-mode from virtual layout test configs.

The flag has no effect.

Also delete the targetedstylerecalc virtual test suite, since that feature has now launched.

BUG=

Review URL: https://codereview.chromium.org/360823002

git-svn-id: svn://svn.chromium.org/blink/trunk@177257 bbb929c8-8fbe-4397-9dbb-9b2b20218538