Execute sphinx-build directly, delete Makefile

Author: bittner

docs/Makefile

@@ -30,9 +30,7 @@ commands = pyclean {posargs:. --debris --erase docs/_build/**/* docs/_build/ tes
 description = Build package documentation (HTML)
 skip_install = true
 deps = sphinx
-changedir = docs
-commands = make html
-allowlist_externals = make
+commands = sphinx-build -M html docs docs/_build
 
 [testenv:format]
 description = Ensure consistent code style (Ruff)