fix(cli): show adk create --type in --help

Remove hidden=True so the documented option appears in --help.

Fixes #6737

Author: ktz03

src/google/adk/cli/cli_tools_click.py

@@ -684,7 +684,6 @@ def cli_conformance_test(
     ),
     default="CODE",
     show_default=True,
-    hidden=True,  # Won't show in --help output. Not ready for use.
 )
 @click.argument("app_name", type=str, required=True)
 def cli_create_cmd(