Merge pull request yt-project#99 from chrishavlin/fix_failing_docs_build

update readthedocs config

.readthedocs.yml

@@ -9,15 +9,21 @@ version: 2
 sphinx:
   configuration: docs/conf.py
 
+# Specify the build os and python version
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.9"
+
 # Build documentation with MkDocs
 #mkdocs:
 #  configuration: mkdocs.yml
 
 # Optionally build your docs in additional formats such as PDF
 formats: []
 
-# Optionally set the version of Python and requirements required to build your docs
+
+# Optionally set the Python requirements required to build your docs
 python:
-  version: 3.7
   install:
-    - requirements: docs/requirements.txt
+  - requirements: docs/requirements.txt