Update Growatt quality scale: mark docs rules done and exempt discovery

[johanzander]

Proposed change

Update quality_scale.yaml for the Growatt integration to reflect the current state of the documentation and integration type:

• Mark all gold-level documentation rules as done — the live documentation at https://www.home-assistant.io/integrations/growatt_server already covers all required sections (data updates, examples, known limitations, supported devices, supported functions, troubleshooting, and use cases).
• Mark discovery and discovery-update-info as exempt — Growatt is a cloud_polling integration that communicates with Growatt cloud servers, not local inverter hardware, so local device discovery protocols (mDNS, SSDP, DHCP, etc.) do not apply.

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:
• Link to developer documentation pull request:
• Link to frontend pull request:

Checklist

• I understand the code I am submitting and can explain how it works.
• 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.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.
• 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

If the code communicates with devices, web services, or third-party tools:

• 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.
• For the updated dependencies a diff between library versions and ideally a link to the changelog/release notes is added to the PR description.

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