Remove references to libpeerconnection.
Remove references to libpeerconnection.

What used to be the libpeerconnection library is now compiled
statically into the Chromium binary, so clean up references it.

BUG=chromium:482123
TBR=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1399513002 .

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#10216}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 6ffc3309dee47b31ba118e41acc89a258c754c33

jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,aleonliao/webrtc-trunk,aleonliao/webrtc-trunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,aleonliao/webrtc-trunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,aleonliao/webrtc-trunk,jchavanton/webrtc,aleonliao/webrtc-trunk,aleonliao/webrtc-trunk,jchavanton/webrtc,jchavanton/webrtc