fix(jenkins): reset baseUrl in protractor conf

Commit 22b817e changed the url
used by protractor in all docs tests to prepend "build/docs", which
was already set to the `baseUrl` in `protractor-jenkins.conf`. This
commit just changes the protractor config's `baseUrl` to adapt
to the changes in the spec files.

Closes angular#9783

protractor-jenkins-conf.js

@@ -13,7 +13,7 @@ exports.config = {
     'browserName': 'chrome'
   },
 
-  baseUrl: 'http://localhost:8000/build/docs/',
+  baseUrl: 'http://localhost:8000/',
 
   framework: 'jasmine',