Update to be compatible with newer version of Sphinx
(A year a go)[https://github.com/sphinx-doc/sphinx/commit/c73628dfcac844f89198ccd805e8e35609b37636], related to version 7.3.5, the require_sphinx method starting enforcing major.minor
format on the input.
By conforming to this format, the project will work again with newer versions of Sphinx.
Thanks for a great piece of code!