fix: Pin Sphnix version to last working release (#51)

Co-authored-by: larkee <larkee@users.noreply.github.com>

Author: larkee

noxfile.py

@@ -143,7 +143,7 @@ def docs(session):
  """Build the docs for this library."""
 
  session.install("-e", ".")
- session.install("sphinx", "alabaster", "recommonmark")
+ session.install("sphinx==2.4.4", "alabaster", "recommonmark")
 
  shutil.rmtree(os.path.join("docs", "_build"), ignore_errors=True)
  session.run(