Fixed aliases type in test.

Author: kmvanbrunt

tests/test_commandset.py

@@ -99,7 +99,7 @@ def do_main(self, args: argparse.Namespace) -> None:
     subcmd_parser = cmd2.Cmd2ArgumentParser(description="Sub Command")
 
     # Include aliases to cover the alias check in cmd2's check_parser_uninstallable().
-    @cmd2.as_subcommand_to('main', 'sub', subcmd_parser, help="sub command", aliases="sub_alias")
+    @cmd2.as_subcommand_to('main', 'sub', subcmd_parser, help="sub command", aliases=["sub_alias"])
     def subcmd_func(self, args: argparse.Namespace) -> None:
         self._cmd.poutput("Subcommand Ran")