Fix the description of paramter '--topics' for play (#1426)

* Fix the description of paramter '--topics' for play

Signed-off-by: Barry Xu <barry.xu@sony.com>

* Adjust description for the player's --topics parameter

Signed-off-by: Michael Orlov <morlovmr@gmail.com>
Co-authored-by: Tomoya.Fujita <Tomoya.Fujita@sony.com>

* Address comments

Signed-off-by: Barry Xu <barry.xu@sony.com>

---------

Signed-off-by: Barry Xu <barry.xu@sony.com>
Signed-off-by: Michael Orlov <morlovmr@gmail.com>
Co-authored-by: Michael Orlov <morlovmr@gmail.com>
Co-authored-by: Tomoya.Fujita <Tomoya.Fujita@sony.com>

ros2bag/ros2bag/verb/play.py

@@ -50,8 +50,7 @@ def add_arguments(self, parser, cli_name):  # noqa: D102
             help='rate at which to play back messages. Valid range > 0.0.')
         parser.add_argument(
             '--topics', type=str, default=[], nargs='+',
-            help='topics to replay, separated by space. If none specified, all topics will be '
-                 'replayed.')
+            help='Space-delimited list of topics to play.')
         parser.add_argument(
             '-e', '--regex', default='',
             help='filter topics by regular expression to replay, separated by space. If none '