Proposed change

Update the mfa setup schema so that voluptuous_serialize can serialize it. Previously, it was failing and making it impossible to set up MFA notify:

  File "/usr/src/homeassistant/homeassistant/components/auth/mfa_setup_flow.py", line 117, in async_setup_flow
    websocket_api.result_message(msg["id"], _prepare_result_json(result))
                                            ~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/auth/mfa_setup_flow.py", line 163, in _prepare_result_json
    data["data_schema"] = voluptuous_serialize.convert(schema)
                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/voluptuous_serialize/__init__.py", line 59, in convert
    pval = convert(value, custom_serializer=custom_serializer)
  File "/usr/local/lib/python3.13/site-packages/voluptuous_serialize/__init__.py", line 164, in convert
    raise ValueError(f"Unable to convert schema: {schema}")
ValueError: Unable to convert schema: <class 'str'>

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:
• Link to developer documentation pull request:
• Link to frontend pull request:

Checklist

• I understand the code I am submitting and can explain how it works.
• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.
• Any generated code has been carefully reviewed for correctness and compliance with project standards.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.