Modernize documentation links

Summary:
  - Point them at the new Diviner.
  - Make them a little less cumbersome to write.

Test Plan: Found almost all of these links in the UI and clicked them.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D8553

src/applications/diffusion/controller/DiffusionRepositoryEditHostingController.php

@@ -91,7 +91,7 @@ final class DiffusionRepositoryEditHostingController
         ->setValue($v_hosting);
 
     $doc_href = PhabricatorEnv::getDoclink(
-      'article/Diffusion_User_Guide_Repository_Hosting.html');
+      'Diffusion User Guide: Repository Hosting');
 
     $form = id(new AphrontFormView())
       ->setUser($user)