Remove deprecated yaml import for Russound RIO

[noahhusby]

Breaking change

The Russound RIO integration was migrated to a config flow in HA 2024.8. The deprecation is slated for removal in 2025.2 as completed in this PR.

Proposed change

SSIA

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:

Checklist

• The code change is tested and works locally.
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• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

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[gjohansson-ST]

There are conflicts that needs to be addressed, please click "ready for review" once rebased.

[home-assistant]

Please take a look at the requested changes, and use the Ready for review button when you are done, thanks 👍

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[gjohansson-ST]

Thanks @noahhusby 👍