WebRTC: Remove references to src/third_party/libjingle/source/talk

A while back, we removed the last pieces of code in
src/third_party/libjingle/source/talk and it is no longer synced
in Chromium's DEPS file. Clean this up to avoid confusion in the
buildbot recipes.

BUG=webrtc:4256

Review-Url: https://codereview.chromium.org/2325043002

recipe_modules/gclient/config.py

@@ -389,8 +389,6 @@ def chromium_skia(c):
 
 @config_ctx(includes=['chromium'])
 def chromium_webrtc(c):
-  c.got_revision_mapping['src/third_party/libjingle/source/talk'] = (
-      'got_libjingle_revision')
   c.got_revision_mapping['src/third_party/libvpx/source'] = (
       'got_libvpx_revision')
 
@@ -404,7 +402,6 @@ def chromium_webrtc_tot(c):
   """
   c.revisions['src'] = 'HEAD'
   c.revisions['src/third_party/webrtc'] = 'HEAD'
-  c.revisions['src/third_party/libjingle/source/talk'] = 'HEAD'
 
 @config_ctx()
 def webrtc_test_resources(c):