Krzysztof Gogolewski authored Sep 25, 2020 and Marge Bot committed Sep 25, 2020

* Remove UnliftedFFITypes from conf. Some time ago, this extension
  was undocumented and we had to silence a warning.
  This is no longer needed.
* Use r'' in conf.py. This fixes a Sphinx warning:
  WARNING: Support for evaluating Python 2 syntax is deprecated and will be removed in Sphinx 4.0. Convert docs/users_guide/conf.py to Python 3 syntax.
* Mark GHCForeignImportPrim as documented
* Fix formatting in template_haskell.rst
* Remove 'recursive do' from the list of unsupported items in TH