Bump tree-sitter to 0.20.4

What does this merge request do and why?

This bumps tree-sitter core (not grammars) from 0.20.1 to 0.20.4.

• Full changelog.
• Tracked core changes

Scanning through the change log, I don't see anything stand out apart from new bindings. However, we do not use these in this repo.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.