Update concepts/none/introduction.md

Co-authored-by: Yrahcaz <74512479+Yrahcaz7@users.noreply.github.com>

Author: BethanyG

concepts/none/introduction.md

@@ -19,7 +19,7 @@ type(a)
 def add_to_todos(new_task, todo_list=None):
     if todo_list is None:
         todo_list = []  
-     todo_list.append(new_task)
+    todo_list.append(new_task)
 
   return todo_list
 ```