Add navabi to OWNERS for build/android/pylib.

3 out of 4 existing owners have since left Chrome.

BUG=

Review URL: https://codereview.chromium.org/299623005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271863 0039d316-1c4b-4281-b951-d872f2087c98

build/android/pylib/OWNERS

 bulach@chromium.org
 craigdh@chromium.org
 frankf@chromium.org
+navabi@chromium.org
 pliard@chromium.org