Don't sign releases to PyPI anymore

Re https://blog.pypi.org/posts/2023-05-23-removing-pgp/

Author: bitprophet

tasks.py

@@ -120,7 +120,6 @@ def regression(c, jobs=8):
             "find_opts": "-and -not \( -path './invoke/vendor*' -or -path './build*' \)"  # noqa
         },
         "packaging": {
-            "sign": True,
             "wheel": True,
             "check_desc": True,
             "changelog_file": os.path.join(