CLI: update subcommands to use return instead of exit() (#10323)

lib/python/qmk/cli/list/keymaps.py

@@ -15,7 +15,7 @@ def list_keymaps(cli):
     """
     if not is_keyboard(cli.config.list_keymaps.keyboard):
         cli.log.error('Keyboard %s does not exist!', cli.config.list_keymaps.keyboard)
-        exit(1)
+        return False
 
     for name in qmk.keymap.list_keymaps(cli.config.list_keymaps.keyboard):
         print(name)