Remove stevenjb@ from webui OWNERS

* cr_elements/OWNERS would be left with one owner (michaelpg@),
  which we try to avoid, and who is not actively working on the webui
  platform at this time. Therefore the file was just removed.
* webui/resources/OWNERS had some stale rules and a similar problem
  so was also removed.

OWNERS for these directories will now resolve to
ui/webui/PLATFORM_OWNERS.

Bug: 1055481
Change-Id: I48d68399f2b97a9bc3e5ee5ea98c7b6fc6fee5d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2074814Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744837}

ui/webui/resources/OWNERS

-per-file cr_elements_*=michaelpg@chromium.org
-per-file cr_elements_*=stevenjb@chromium.org
-per-file polymer_resources.grdp=michaelpg@chromium.org

ui/webui/resources/cr_components/OWNERS

 dpapad@chromium.org
 khorimoto@chromium.org
-stevenjb@chromium.org

ui/webui/resources/cr_elements/OWNERS

-michaelpg@chromium.org
-stevenjb@chromium.org