Update lower-level codereview.settings files.

Every now and then we get CLs to codereview.webrtc.org
that are created from a Chromium checkout by editing
the code in third_party/webrtc or third_party/libjingle.

By editing these lower-level codereview.settings files,
we instead cause a crash during 'git cl upload', but the
contents of the file will also be printed, which can work
as an error message. The alternative would be to entirely
remove the files.

BUG=
R=andrew@webrtc.org, tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1389963002 .

Cr-Commit-Position: refs/heads/master@{#10191}
diff --git a/talk/codereview.settings b/talk/codereview.settings
index c138ebb..97bee14 100644
--- a/talk/codereview.settings
+++ b/talk/codereview.settings
@@ -1,10 +1,4 @@
-# This file is used by gcl to get repository specific information.
-CODE_REVIEW_SERVER: codereview.webrtc.org
-CC_LIST: webrtc-reviews@webrtc.org
-VIEW_VC: https://chromium.googlesource.com/external/webrtc/+/
-TRY_ON_UPLOAD: False
-TRYSERVER_SVN_URL: svn://svn.chromium.org/chrome-try/try-webrtc
-TRYSERVER_PROJECT: webrtc
-TRYSERVER_ROOT: src/talk
-PROJECT: webrtc
-PENDING_REF_PREFIX: refs/pending/
+
+Creating CLs from this location is not supported!
+Please create a full WebRTC checkout using 'fetch webrtc'
+or by cloning https://chromium.googlesource.com/external/webrtc