Remove no longer relevant parameters to transition tests

This patch removes the should(Not)BeTransitioning argument from
transition tests, since it is no longer handled by the helper script.
Properly checking whether properties are transitioning requires a bit of
plumbing, and provides little in the way of improved testing.

BUG=235752

Review URL: https://codereview.chromium.org/51673003

git-svn-id: svn://svn.chromium.org/blink/trunk@160893 bbb929c8-8fbe-4397-9dbb-9b2b20218538