Tweaks to model release checklist

[julien-c]

• Renames a section header from “Uploading models” to “Uploading weights”
• Improves grammar in best practices statements and updates guide links
• Reorders the mixin class adoption instructions for enhanced clarity

[Copilot]

Pull Request Overview

This PR makes tweaks to the model release checklist documentation to clarify instructions and update links.

• Renames a section header from “Uploading models” to “Uploading weights”
• Improves grammar in best practices statements and updates guide links
• Reorders the mixin class adoption instructions for enhanced clarity

Comments suppressed due to low confidence (1)

docs/hub/model-release-checklist.md:7

• The section header 'Uploading weights' appears inconsistent with the content that discusses uploading models. Consider renaming it to 'Uploading models' or updating the subsequent text for clarity.

### Uploading weights

[HuggingFaceDocBuilderDev]

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