Add brucedawson@ as presubmit*.py OWNER

I feel like a PRESUBMIT owner now and this makes it official.

Bug: 1309977
Change-Id: I38356bc52c8d03d93c4ec42e4952b5872b31a79a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3589901
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>

OWNERS

@@ -12,6 +12,8 @@ per-file ninja*=thakis@chromium.org
 per-file autoninja*=brucedawson@chromium.org
 per-file post_build_ninja_summary.py=brucedawson@chromium.org
 
+per-file presubmit*.py=brucedawson@chromium.org
+
 per-file ninjalog*=tikuta@chromium.org
 
 per-file pylint*=vapier@chromium.org