Fix documentation snippets

Author: fwcd

bindings/rust/README.md

@@ -17,6 +17,6 @@ let code = r#"
   )
 "#;
 let mut parser = Parser::new();
-parser.set_language(tree_sitter_kotlin::language()).expect("Error loading Kotlin grammar");
+parser.set_language(&tree_sitter_kotlin::language()).expect("Error loading Kotlin grammar");
 let parsed = parser.parse(code, None);
 ```

bindings/rust/lib.rs

@@ -6,7 +6,7 @@
 //! ```
 //! let code = "";
 //! let mut parser = tree_sitter::Parser::new();
-//! parser.set_language(tree_sitter_kotlin::language()).expect("Error loading kotlin grammar");
+//! parser.set_language(&tree_sitter_kotlin::language()).expect("Error loading kotlin grammar");
 //! let tree = parser.parse(code, None).unwrap();
 //! ```
 //!