bug: "u{[0-9a-fA-F]+}" in grammar.json leads to regex parse error

[polyzen]

Did you check existing issues?

• [ ] I have read all the tree-sitter docs if it relates to using the parser
• [X] I have searched the existing issues

Tree-Sitter CLI Version, if relevant (output of tree-sitter --version)

tree-sitter 0.22.2 (fc15f621334a262039ffaded5937e2844f88da61)

Describe the bug

tree-sitter generate --no-bindings src/grammar.json errors out with:

Error processing rule escape_sequence

Caused by:
    regex parse error:
        u{[0-9a-fA-F]+}
          ^
    error: repetition quantifier expects a valid decimal

Steps To Reproduce/Bad Parse Tree

1. Clone repo
2. Run tree-sitter generate --no-bindings src/grammar.json

Expected Behavior/Parse Tree

No error

Repro

No response