Removing deadbeef@ from OWNERS files.

Since I'm leaving Google.

NOTRY=True

Bug: None
Change-Id: I4c9d75d20e0168d16b064c661f8f15e9c510a592
Reviewed-on: https://chromium-review.googlesource.com/1121355Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571838}

content/renderer/p2p/OWNERS

 sergeyu@chromium.org
 juberti@chromium.org
-deadbeef@chromium.org
 
 # COMPONENT: Blink>WebRTC

third_party/usrsctp/OWNERS

 pthatcher@chromium.org
-deadbeef@chromium.org
 jiayl@chromium.org
 ldixon@chromium.org