Fix race in dlna_dmr test

[bdraco]

Proposed change

The entity was removed before the entity registry could update it

Traceback (most recent call last):
  File "/Users/bdraco/home-assistant/homeassistant/helpers/entity.py", line 1482, in _async_process_registry_update_or_remove
    assert registry_entry is not None
AssertionError

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 documentation pull request:

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[home-assistant]

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

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[bdraco]

thanks