Update OWNERS of chrome/common/media/ to reference /media OWNERS

As the code is all related to media, use the /media OWNERS for changes
rather than relying on chrome/common/ OWNERS.

Bug: none
Change-Id: I44b225b35bb409e38eaa8fe8423e6752ba96dd32
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1823799Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: John Rummell <jrummell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699965}

chrome/common/media/OWNERS

+file://media/OWNERS
+
 per-file *_messages*.h=set noparent
 per-file *_messages*.h=file://ipc/SECURITY_OWNERS