Fix grammar

[danieltrt]

The tree-sitter parser generator is interpreting the newline token as a regular token. As a result there are artifacts in the grammar when parsing go code (i.e., \n shows up as a node). This messes concrete's syntax ability to match multiline code blocks

Checklist:

• All tests pass in CI.
• There are sufficient tests for the new fix/feature.
• Grammar rules have not been renamed unless absolutely necessary.
• The conflicts section hasn't grown too much.
• The parser size hasn't grown too much (check the value of STATE_COUNT in src/parser.c).