Remove mirandac from OWNERS since she no longer works on chrome.

BUG=none
R=mirandac@chromium.org

Review URL: https://codereview.chromium.org/25612003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226342 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226342