{iot} az iot dps access-policy: Defer its deprecation

[jiasli]

Fix #20682 (comment)

az iot dps access-policy command group's deprecation in 2.35.0 caused lots of linter failure after upgrading Azure CLI to 2.35.0:

https://dev.azure.com/azure-sdk/public/_build/results?buildId=1475423&view=logs&j=168ccbe3-da49-5c0b-6478-08f7016e4bf5&t=10a595be-4223-5cc7-9a73-012871b6eaee

-  FAIL - HIGH severity: faulty_help_example_parameters_rule
    Help-Entry: `iot dps access-policy create` - 
	There is a violation:
	"az iot dps access-policy create --dps-name MyDps --resource-group MyResourceGroup --name MyPolicy --rights EnrollmentRead" is not a valid command.
	argument _subcommand: unknown parser 'access-policy' (choices: list, show, create, delete, update, linked-hub, certificate, policy).
...
-  FAIL - HIGH severity: expired_command_group
    Command-Group: `iot dps access-policy` - Deprecated command group is expired and should be removed.
...
-  FAIL - HIGH severity: missing_command_help
    Command: `iot dps access-policy create` - Missing help
    Command: `iot dps access-policy delete` - Missing help
    Command: `iot dps access-policy list` - Missing help
    Command: `iot dps access-policy show` - Missing help
    Command: `iot dps access-policy update` - Missing help

This PR defers the deprecation.

@c-ryan-k, @zhoxing-ms, please do make sure this command group is removed in 2.36.0.