docs: Minor clean up of Phabricator documentation.

llvm-svn: 165779
diff --git a/llvm/docs/userguides.rst b/llvm/docs/userguides.rst
index 94f7218..8c1554d 100644
--- a/llvm/docs/userguides.rst
+++ b/llvm/docs/userguides.rst
@@ -19,6 +19,7 @@
    yaml2obj
    HowToSubmitABug
    SphinxQuickstartTemplate
+   Phabricator
 
 * :ref:`getting_started`