Small documentation fix

[huntipl]

Thank you for submitting this pull request! We appreciate you spending the time to work on these changes.

What is the motivation?

Found a small issue in the documentation that can cause confusion when writing custom queries, the old version before rewrite was correct

Type of Change

• 📚 Examples / docs / tutorials / dependencies update
• 🔧 Bug fix (non-breaking change which fixes an issue)
• 🥂 Improvement (non-breaking change which improves an existing feature)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🔐 Security fix

What does this change do?

Added a missing character to the Readme

What is your testing strategy?

Verified locally that adding $ sign to the query fixes the issue in the documentation

Is this related to any issues?

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines