Fix readthedocs build error

.readthedocs.yaml

@@ -1,6 +1,11 @@
 # Required
 version: 2
 
+build:
+  os: ubuntu-22.04
+   tools:
+     python: "3.8"
+
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
    configuration: docs/source/conf.py
@@ -11,9 +16,7 @@ sphinx:
 # formats:
 #   - pdf
 
-# Optionally set the version of Python and requirements required to build your docs
 python:
-   version: 3.8
    install:
    - requirements: docs/requirements.txt
    - requirements: requirements.txt