Stop uploading GPG signatures to pypi since it no longer supports them.

scripts/release

@@ -35,10 +35,8 @@ git push github $version
 rm -fr dist
 python3 setup.py bdist_wheel
 python3 setup.py sdist
-gpg --detach-sign --armor dist/borgmatic-*.tar.gz
-gpg --detach-sign --armor dist/borgmatic-*-py3-none-any.whl
-twine upload -r pypi --username __token__ dist/borgmatic-*.tar.gz dist/borgmatic-*.tar.gz.asc
-twine upload -r pypi --username __token__ dist/borgmatic-*-py3-none-any.whl dist/borgmatic-*-py3-none-any.whl.asc
+twine upload -r pypi --username __token__ dist/borgmatic-*.tar.gz
+twine upload -r pypi --username __token__ dist/borgmatic-*-py3-none-any.whl
 
 # Set release changelogs on projects.torsion.org and GitHub.
 release_changelog="$(cat NEWS | sed '/^$/q' | grep -v '^\S')"