Remove force compositing PhysicalTestSuite settings

These are redundant as force compositing mode is on by default.

BUG=361729

Review URL: https://codereview.chromium.org/328503002

git-svn-id: svn://svn.chromium.org/blink/trunk@175928 bbb929c8-8fbe-4397-9dbb-9b2b20218538