Remove mojom_data_tests.py.

This was missed in r230861 (revert of r230837).

TBR=ajwong@chromium.org,viettrungluu@chromium.org
BUG=None

Review URL: https://codereview.chromium.org/42093005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230890 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230890