Remove outdated pandoc step from docs

The pypi description now can read markdown directly with the appropriate
setup.py configuration. (which we already have)

Author: carver

docs/contributing.rst

@@ -99,24 +99,6 @@ feature or bugfix.
 Releasing
 ~~~~~~~~~
 
-One time setup
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Pandoc is required for transforming the markdown README to the proper
-format to render correctly on pypi.
-
-For Debian-like systems:
-
-::
-
-    apt install pandoc
-
-Or on OSX:
-
-.. code:: sh
-
-    brew install pandoc
-
 Final test before each release
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^