Remove csharp from chrome _cleaner/OWNERS

Change-Id: I71975e2b88bf5178febd03cc079fb549814b8091
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1727209
Commit-Queue: Chris Sharp <csharp@chromium.org>
Commit-Queue: proberge <proberge@chromium.org>
Auto-Submit: Chris Sharp <csharp@chromium.org>
Reviewed-by: proberge <proberge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682438}

chrome/chrome_cleaner/OWNERS

-csharp@chromium.org
 joenotcharles@google.com
 proberge@chromium.org