Improve informative message in codereview.settings.

In https://codereview.webrtc.org/1389963002 the message
displayed when trying to create a CL from an unsupported
location was improved. However it's confusing for developers
working from a WebRTC checkout if they stand in src/webrtc
when trying to create a CL.

R=henrika@webrtc.org, phoglund@webrtc.org

Review URL: https://codereview.webrtc.org/1432073002 .

Cr-Commit-Position: refs/heads/master@{#10571}
diff --git a/talk/codereview.settings b/talk/codereview.settings
index 97bee14..c441cc6 100644
--- a/talk/codereview.settings
+++ b/talk/codereview.settings
@@ -1,4 +1,5 @@
 
-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
+Creating CLs from this location is not supported! Please make sure the current
+working directory is the parent directory of this directory.
+If you're working with a Chromium checkout, you'll have to create a full WebRTC
+checkout and upload a CL from that. See http://www.webrtc.org for instructions.