pip install rst-to-myst sphinx DOWNGRADES Sphinx v8 to v6

[cclauss]

Describe the bug

context
When I do pip install rst-to-myst sphinx.

expectation
I expected Sphinx v8 to be installed.

bug
But instead, Sphinx v6 is installed.
Here's an error message I ran into...
% pip list | grep Sphinx

Sphinx 6.2.1

problem
This is a problem for people who want to use the current Sphinx.

Reproduce the bug

% pip install rst-to-myst sphinx && pip list | grep Sphinx
Sphinx 6.2.1

List your environment

Sphinx 6.2.1