Delete tests/__init__.py. It should have been deleted in r109636 but the CQ failed.

R=dpranke@chromium.org
BUG=
TEST=


Review URL: http://codereview.chromium.org/8536018

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@109697 0039d316-1c4b-4281-b951-d872f2087c98