Added back help on root file

Author: briantkim-msft

src/nginx/azext_nginx/aaz/latest/nginx/deployment/configuration/_update.py

@@ -90,6 +90,7 @@ def _build_arguments_schema(cls, *args, **kwargs):
         _args_schema.root_file = AAZStrArg(
             options=["--root-file"],
             arg_group="Properties",
+            help="The root file of the Nginx Configuration"
             nullable=True,
         )