Fix build docs action

[rwedge]

The "build docs" github action is currently failing on main

Stacktrace:

make: Entering directory '/home/runner/work/featuretools/featuretools/docs'
rm -rf build/*
rm -rf source/generated/*
sphinx-build -b html -d build/doctrees  -W source build/html
Running Sphinx v3.2.1
WARNING:root:'PYARROW_IGNORE_TIMEZONE' environment variable was not set. It is required to set this environment variable to '1' in both driver and executor sides if you use pyarrow>=2.0.0. Koalas will set it for you but it does not work if there is a Spark context already launched.

Warning, treated as error:
node class 'meta' is already registered, its visitors will be overridden
make: *** [Makefile:60: html] Error 2
make: Leaving directory '/home/runner/work/featuretools/featuretools/docs'
Error: Process completed with exit code 2.

PYARROW warning has been around for a while, the "node class ..." warning is new and seems to be the issue

Link to recent run: https://github.com/alteryx/featuretools/runs/4023950259?check_suite_focus=true

[thehomebrewnerd]

docutils was recently updated and caused build issues in other repos. Not sure if it could be causing an issue here as well, since the error message is different, but might try building with docutils pinned to 0.17.1 to see if that fixes the issue here as well.

[rwedge]

sphinx-doc/sphinx#9777

Latest sphinx version pins docutils for us, might be a good time to upgrade our dev dependencies