Loosen tree-sitter dependency versions (#379)

* Loosen tree-sitter dependency versions

`tree-sitter` has released changes that are breaking within its library
itself, but that do not bump the ABI_VERSION. This means that although
the `tree-sitter` "major version" has changed, this is compatible across
major versions.

Cargo.toml

@@ -20,10 +20,11 @@ include = [
 path = "bindings/rust/lib.rs"
 
 [dependencies]
-tree-sitter = "^0.20.4"
+tree-sitter = ">=0.20.4, <0.23.0"
 
 [build-dependencies]
 cc = "1.0"
 
 [dev-dependencies]
 anyhow = "1.0"
+tree-sitter = "0.20.4"