Improve tests of mqtt device triggers

[jbouwh]

Proposed change

Improve the quality of the tests of MQTT device triggers. Correct test where the type or subtype of the attached trigger differs from the type and subtype in the device automation and only is linked to the discovery_id.

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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[home-assistant]

There is a merge conflict.

[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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[home-assistant]

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

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rebased