Fixed dash-separated deprecation warning in setup.cfg.

Deprecated in setuptools 54.1.0.

setup.cfg

@@ -51,7 +51,7 @@ bcrypt = bcrypt
 
 [bdist_rpm]
 doc_files = docs extras AUTHORS INSTALL LICENSE README.rst
-install-script = scripts/rpm-install.sh
+install_script = scripts/rpm-install.sh
 
 [flake8]
 exclude = build,.git,.tox,./tests/.env