Use header-subtitle in dialog-edit-home

[pcan08]

Proposed change

Replace the custom <p class="description"> element and its associated CSS with the built-in headerSubtitle property on ha-dialog.

It simplifies the code, avoid specific CSS and reuse dialog capability that seems appropriate here. Moreover, it allows to gain space in the dialog.

This is related to #51401 (comment), so this PR should be considered as a step to improve the home dashboard settings dialog look and feel.

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Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• 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 or discussion:
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Checklist

• I understand the code I am submitting and can explain how it works.
• The code change is tested and works locally.
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• Any generated code has been carefully reviewed for correctness and compliance with project standards.

If user exposed functionality or configuration variables are added/changed:

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

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.