docs: fix compatibilityDate value

[yamanoku]

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 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)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The compatibilityDate value uses the DateString type and should be in YYYY--MM-DD format, but the documentation incorrectly described it as YY-MM-DD, so I've corrected it.

📝 Checklist

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

[vercel]

@yamanoku is attempting to deploy a commit to the Nitro Team on Vercel.

A member of the Team first needs to authorize it.

[pi0]

Thanks for PR. Can you please rebase your commit against v2 branch

[yamanoku]

@pi0 I’ve rebased and switched it to the v2 branch. Please review.