fix: correct spelling of "Unknown" in ASSERT message for argument type validation

src/wren_vm.c

@@ -1341,7 +1341,7 @@ void wrenCall(WrenVM* vm, WrenMethod* method, const char* argTypes, ...)
       }
 
       default:
-        ASSERT(false, "Uknown argument type.");
+        ASSERT(false, "Unknown argument type.");
         break;
     }