Revert "test: add DummyInput and DummyOutput to TestHelp setup"

This reverts commit d098a4c.

tests/help/test_help.py

@@ -1,9 +1,6 @@
 import unittest
 from unittest.mock import MagicMock
 
-from prompt_toolkit.input import DummyInput
-from prompt_toolkit.output import DummyOutput
-
 import aider
 from aider.coders import Coder
 from aider.commands import Commands
@@ -15,7 +12,7 @@
 class TestHelp(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        io = InputOutput(pretty=False, yes=True, input=DummyInput(), output=DummyOutput())
+        io = InputOutput(pretty=False, yes=True)
 
         GPT35 = Model("gpt-3.5-turbo")