Update Makefile clean action (#1738)

Makefile

@@ -22,6 +22,7 @@ clean:
 	find . -name *.pyc -delete
 	rm -rf .mypy_cache/*
 	rm -rf .pytest_cache/*
+	rm -rf dist/*
 	rm -rf docs/build/*
 	rm -rf docs/source/_autosummary/*