Merge pull request #169 from askpatrickw/rtd-python-ver

correct python version for RTD

Author: kattni

{{ cookiecutter and 'tmp_repo' }}/{% if cookiecutter.sphinx_docs in ['y', 'yes'] %}.readthedocs.yaml{% endif %}

@@ -8,8 +8,12 @@
 # Required
 version: 2
 
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3"
+
 python:
-  version: "3.x"
   install:
     - requirements: docs/requirements.txt
     - requirements: requirements.txt