[CLI] Update help string for sky api status -a (#7804)

* fix help str

* Fix help str

Author: romilbhardwaj

sky/client/cli/command.py

@@ -6369,7 +6369,9 @@ def convert(self, value, param, ctx):
               is_flag=True,
               default=False,
               required=False,
-              help='Show requests of all statuses.')
+              help=('Show requests of all statuses, including finished ones '
+                    '(SUCCEEDED, FAILED, CANCELLED). By default, only active '
+                    'requests (PENDING, RUNNING) are shown.'))
 @click.option(
     '--limit',
     '-l',