Remove miu@chromium.org from OWNERS files.

They left Chromium on 1/6.  In some cases, jophba@ is added as an
additional OWNER.

Change-Id: I28108fe1a331aadc94dcb232d1a0bdb1264b55e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2650631


Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Jordan Bayles <jophba@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Auto-Submit: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#847432}