Attempt to fix RTD failures using Python 3.7

The default Python version has changed from 3.7 to 3.11 when updating
Read the Docs configuration. See the announcement of configuration file
version 2 for more details [1].

[1] https://blog.readthedocs.com/migrate-configuration-v2/

Author: priteau

.readthedocs.yaml

@@ -10,7 +10,7 @@ build:
     - tox
   os: ubuntu-22.04
   tools:
-    python: "3.11"
+    python: "3.7"
 
 # Build documentation in the doc/source/ directory with Sphinx
 sphinx: