Replace links to code.google.com/p/gerrit

Google Code was shut down nearly 2 years ago [1] and the links
don't work any more. Replace them with the new locations.

[1] https://opensource.googleblog.com/2015/03/farewell-to-google-code.html

Change-Id: I53e791d04eb243483d69254a296c30e59a7de479

Documentation/config-sso.txt

@@ -64,7 +64,7 @@ Users wishing to link an alternative identity should *NOT* log in separately
 with that identity. Doing so will result in a new account being created, and
 subsequent attempts to link that account with the existing account will fail.
 In cases where this happens, the administrator will need to manually merge the
-accounts.  See link:https://code.google.com/p/gerrit/wiki/SqlMergeUserAccounts[
+accounts.  See link:https://gerrit.googlesource.com/homepage/+/md-pages/docs/SqlMergeUserAccounts.md[
 Merging Gerrit User Accounts] on the Gerrit Wiki for details.
 
 Linking another identity is also useful for users whose primary OpenID provider

Documentation/dev-design.txt

@@ -342,7 +342,7 @@ automate interfaces may make it impossible for non-browser agents
 to be used with the JSON-RPC interface.
 
 * link:http://json-rpc.org/wd/JSON-RPC-1-1-WD-20060807.html[JSON-RPC 1.1]
-* link:http://code.google.com/p/gerrit/source/browse/README?repo=gwtjsonrpc&name=master[XSRF JSON-RPC]
+* link:https://gerrit.googlesource.com/gwtjsonrpc/+/master/README[XSRF JSON-RPC]
 
 
 == Privacy Considerations

Documentation/dev-readme.txt

@@ -266,7 +266,7 @@ the browser and on the server side.
 
 Google Web Toolkit:
 
-* http://code.google.com/webtoolkit/download.html[Download]
+* http://www.gwtproject.org/download.html[Download]
 
 Apache SSHD: