python: Remove redundant dest for argparse arguments.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/management/commands/check_redis.py

@@ -17,7 +17,6 @@ class Command(BaseCommand):
 
     def add_arguments(self, parser: CommandParser) -> None:
         parser.add_argument('-t', '--trim',
-                            dest='trim',
                             default=False,
                             action='store_true',
                             help="Actually trim excess")