Set entity category for isy auxiliary sensors

[bdraco]

Proposed change

Set entity category for isy auxiliary sensors

Address @shbatm review comments (#71254 (comment))

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

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
• There is no commented out code in this PR.
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• Tests have been added to verify that the new code works.

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• Documentation added/updated for www.home-assistant.io

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• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
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• Always create the error count sensor (disabled by default)

[probot-home-assistant]

Hey there @shbatm, mind taking a look at this pull request as it has been labeled with an integration (isy994) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[bdraco]

Thanks @shbatm @ctalkington