KNX christmas cleaning #2 - remove old migrations

[marvin-w]

Proposed change

Remove old migrations for unique_ids from April and May respectively.

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)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

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• This PR fixes or closes issue: fixes #
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• Link to documentation pull request:

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• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.

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  Updated and included derived files by running: python3 -m script.hassfest.
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  Updated by running python3 -m script.gen_requirements_all.
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[probot-home-assistant]

Hey there @Julius2342, @farmio, mind taking a look at this pull request as it has been labeled with an integration (knx) you are listed as a code owner for? Thanks!
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[farmio]

please add cover.py migrations

[farmio]

👍