Remove duplicate chromedriver2_unittests target.

All infra has been updated to use chromedriver_unittests instead.
BUG=298192
NOTRY=true

Review URL: https://codereview.chromium.org/116833004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254569 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254569