Reduce precision loss when converting HomeKit temperature

[bdraco]

Proposed change

The utility did rounding, but pyhap can do a better job of this because it knows the step sizes. Remove the rounding in the util and let pyhap handle rounding the values based on the step size. While its impossible to fix every issue with loss of precision but we can at least make it a bit better.

fixes #98578

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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[bdraco]

Thanks