Remove docutils pin

This was added to work around bug 1091333.  A new sphinx has been
released and so this is no longer necessary.

Change-Id: I6ea61a3cc441dd1ca2ced7e2fd837a55b917f76d
diff --git a/test-requirements.txt b/test-requirements.txt
index 13ef291..cd8154b 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,6 +1,5 @@
 hacking>=0.9.2,<0.10
 # needed for doc build
-docutils==0.9.1
 sphinx>=1.1.2,!=1.2.0,<1.3
 python-subunit>=0.0.18
 oslosphinx