Remove deprecated import from stiebel_eltron

[ThyMYthOS]

Breaking change

Remove deprecated import from stiebel_eltron component

Proposed change

Remove functionality that was marked as broken in 2025.11.

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 #
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• Link to frontend pull request:

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[home-assistant]

Hey there @fucm, mind taking a look at this pull request as it has been labeled with an integration (stiebel_eltron) you are listed as a code owner for? Thanks!

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[Copilot]

Pull request overview

This PR removes the deprecated YAML configuration import functionality from the stiebel_eltron integration, which was scheduled for removal in version 2025.11. The changes remove the _async_import function that handled YAML-to-config-entry migration and several related imports.

Key changes:

• Removed _async_import function that handled YAML configuration imports
• Removed imports: SOURCE_IMPORT, FlowResultType, issue_registry, and typing.Any
• Simplified async_setup to only return True since it no longer processes YAML configuration