__init__() takes 2 positional arguments but 3 were given

[thesteve0]

Describe the bug
My sphinx site builds fine with

sphinx-build -M html ./docs/source ./docs/build 

but if I run it with the markdown flag it errors out

> sphinx-build -M markdown ./docs/source ./docs/build 
Running Sphinx v3.5.4

Exception occurred:
  File "/home/spousty/git/fifty-one-doc-sphinx-markdown-builder/fiftyone/venv/lib/python3.9/site-packages/sphinx_markdown_builder/builder.py", line 49, in __init__
    super().__init__(app, env)
TypeError: __init__() takes 2 positional arguments but 3 were given
The full traceback has been saved in /tmp/sphinx-err-ls1_o0el.log, if you want to report the issue to the developers.
Please also report this if it was a user error, so that a better error message can be provided next time.
A bug report can be filed in the tracker at <https://github.com/sphinx-doc/sphinx/issues>. Thanks!

I am trying to run it against https://github.com/voxel51/fiftyone/tree/develop/docs

This error happens whether I run the sphinx-build command natively or if I change the sphinx-build command in the bash file:
https://github.com/voxel51/fiftyone/blob/e7f3eddb408c142b59233571c3a7319c6d1c0fcb/docs/generate_docs.bash#L128

Not really that familiar with sphinx and nothing helpful comes up in Google.

To Reproduce
Make sure to create a python 3.9 environment.
Follow the directions on the sphinx-markdown-builder page
Then follow the instructions to build the doc
https://github.com/voxel51/fiftyone/tree/develop/docs

Expected behavior
I expect the docs to build with md as the output

Environment (please complete the following information):

• Ubuntu
• Version 22.04
• Python 3.9
• sphinx-markdown-builder latest

Additional context
Add any other context about the problem here.

[liran-funaro]

Thanks for taking the time to report.

Running Sphinx v3.5.4

Only Sphinx versions greater than v5.1 are supported.
Please upgrade and update here if it resolves your issue.