docs: Update 1.collections.md file fixing z.Date typo

[ismail9k]

🔗 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

Update the 1.collections.md file by correcting the function name from "z.Date" to the proper lowercase version "z.date".

📝 Checklist

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