[cli] Fix: Use dashes in ui validate flag

- Add ui-validate-io flag with dashes
- Add comment to ui_validate_io as deprecated

This follows the conventions set by other CLI tools

operatorcourier/cli.py

@@ -59,9 +59,15 @@ def verify(self):
         parser.add_argument('source_dir', help='Path of your directory of yaml '
                             'files to bundle. Either set this or '
                             'use the files argument for bundle data.')
-        parser.add_argument('--ui_validate_io',
+        parser.add_argument('--ui-validate-io',
+                            dest='ui_validate_io',
                             help='Validate bundle for operatorhub.io UI',
                             action='store_true')
+        parser.add_argument(# DEPRECATED; BW compatibility
+                            '--ui_validate_io',
+                            dest='ui_validate_io',
+                            help=argparse.SUPPRESS,
+                            action='store_true')
         parser.add_argument('--validation-output', dest='validation_output',
                             help='A file to write validation warnings and errors to'
                                  'in JSON format')