Remove the weak ref for tracking update listeners

[balloob]

Breaking change

Proposed change

This removes the weakref for tracking update listeners. All update listeners return unsubscribe functions and can be automatically removed when a config entry is unloaded using entry.async_on_unload

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.
• Local tests pass. Your PR cannot be merged unless tests pass
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• Tests have been added to verify that the new code works.

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[bdraco]

Testing on production..

[bdraco]

Reloaded a few integrations with listeners, modified some config entries, all good