Remove tfarina@ from OWNERS for //third_party/re2

They do not seem to be currently working on the Chromium project.

Change-Id: I621fb17cd1cff49a7c982771b0746f6b1db87e7e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2140302
Auto-Submit: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757198}

third_party/re2/OWNERS

 mmoroz@chromium.org
-tfarina@chromium.org
 thakis@chromium.org
 # COMPONENT: Internals