Prefer str over String get_function

Co-authored-by: ljedrz <ljedrz@users.noreply.github.com>

dynamic-check/src/objects/frame.rs

@@ -168,7 +168,7 @@ impl Frame {
     ///
     /// Get a function's type from the user defined types in the current scope.
     ///
-    fn get_function(&self, name: &String) -> Option<&FunctionType> {
+    fn get_function(&self, name: &str) -> Option<&FunctionType> {
         self.user_defined_types.get_function_type(name)
     }