fix(nuxi): properly detect hash and tag for upgrade changelog

[harlan-zw]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

When upgrading RC versions, the Changelog link is assuming that nuxt was installed using a version with a git commit as the suffix.

For versions that don't have this, only the last digit is used, so the user gets messages like this:

ℹ Cleaning up generated nuxt files and caches...                                                                                                                                                20:39:36
ℹ Upgraded nuxt version: 3.0.0-rc.8                                                                                                                                                         20:39:36
✔ Successfully upgraded nuxt from 3.0.0-rc.6 to 3.0.0-rc.8                                                                                                                                    20:39:36
ℹ Changelog: https://github.com/nuxt/framework/compare/6...8

This PR fixes the behaviour and links the changelog correctly.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

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