Remove myself from WebAudio and platform/audio OWNERS.

I haven't made contributions to this area of the code for a long time.

Bug: none
Change-Id: I7aa03680fe8f087677c11a57fa519e790ba2f2d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2007654
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732960}

third_party/blink/renderer/modules/webaudio/OWNERS

 hongchan@chromium.org
-kbr@chromium.org
 rtoy@chromium.org
 
 # COMPONENT: Blink>WebAudio

third_party/blink/renderer/platform/audio/OWNERS

 hongchan@chromium.org
-kbr@chromium.org
 rtoy@chromium.org
 
 # COMPONENT: Blink>WebAudio