gh-100676: Improve description for venv --upgrade-deps (GH-100678)

Author: rblcoder

Lib/venv/__init__.py

@@ -523,7 +523,7 @@ def main(args=None):
                              'this environment.')
     parser.add_argument('--upgrade-deps', default=False, action='store_true',
                         dest='upgrade_deps',
-                        help=f'Upgrade core dependencies: {" ".join(CORE_VENV_DEPS)} '
+                        help=f'Upgrade core dependencies: {", ".join(CORE_VENV_DEPS)} '
                              'to the latest version in PyPI')
     options = parser.parse_args(args)
     if options.upgrade and options.clear: