repo_gpg options are deprecated but aren't supported at the model level

[jlsherrill]

Version
3.41.0

Describe the bug
#3298 deprecated the gpg key options, but i believe removed support at the model level by accident.
If you try to create a repo with these options, you get:

pulp [4762e7fd09404023ba8a793973d817bb]: pulp_rpm.deprecation:INFO: Support for gpg options will be removed from a future release of pulp_rpm.
pulp [4762e7fd09404023ba8a793973d817bb]: django.request:ERROR: Internal Server Error: /pulp/b52ad510/api/v3/repositories/rpm/rpm/
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 962, in create
    instance = ModelClass._default_manager.create(**validated_data)
  File "/usr/local/lib/python3.8/site-packages/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/db/models/query.py", line 656, in create
    obj = self.model(**kwargs)
  File "/usr/local/lib/python3.8/site-packages/django_lifecycle/mixins.py", line 76, in __init__
    super().__init__(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/db/models/base.py", line 567, in __init__
    raise TypeError(
TypeError: RpmRepository() got unexpected keyword arguments: 'gpgcheck', 'repo_gpgcheck'

During handling of the above exception, another exception occurred:

Initially i thought this was an api issue (and the options were removed), but after looking at the Pr they were actually intended to be deprecated.

To Reproduce
Steps to reproduce the behavior:

use the rpm repository create api to create a repository with one of the deprecated gpg key options:
https://docs.pulpproject.org/pulp_rpm/restapi.html#tag/Repositories:-Rpm/operation/repositories_rpm_rpm_create

Expected behavior
The deprecated options don't cause an ISE, and continue to work (while they are deprecated)

Additional context
Add any other context about the problem here. Please provide links to any previous discussions via Discourse or Bugzilla.