DOC fix warnings

doc/install.txt

@@ -59,8 +59,7 @@ The following libraries and software are optional:
     `Git <http://git-scm.com>`_
         To download bleeding-edge versions of Theano.
 
-    `graphiz <http://www.graphviz.org/>`__ and either
-    ``pydot-ng <https://github.com/pydot/pydot-ng>`_ or `pydot <https://code.google.com/p/pydot/>`_
+    `graphiz <http://www.graphviz.org/>`__ and either `pydot-ng <https://github.com/pydot/pydot-ng>`__ or `pydot <https://code.google.com/p/pydot/>`__
         To be able to make picture of Theano computation graph.
 	pydot-ng is a pydot compatible replacement that support newer Python.