aider: Fixed call to Coder class in tests/test_commands.py.

# Context:
USER: I ran this command:

 pytest tests/test_commands.py

Which produced this output:

============================= test session starts ==============================
platform darwin -- Python 3.11.3, pytest-7.3.1, pluggy-1.0.0
rootdir: /Users/gauthier/Projects/aider
collected 1 item

tests/test_commands.py F                                                 [100%]

=================================== FAILURES ===================================
__________________________ TestCommands.test_cmd_add ___________________________

self = <tests.test_commands.TestCommands testMethod=test_cmd_add>

    def test_cmd_add(self):
        with tempfile.TemporaryDirectory() as tmpdir:
            io = IO(pretty=False, yes=True)
>           coder = Coder(root=tmpdir)
E           TypeError: Coder.__init__() got an unexpected keyword argument 'root'

tests/test_commands.py:13: TypeError
=========================== short test summary info ============================
FAILED tests/test_commands.py::TestCommands::test_cmd_add - TypeError: Coder....
============================== 1 failed in 0.52s ===============================

ASSISTANT: It seems like the `Coder` class in `aider/coder.py` does not accept a `root` keyword argument in its `__init__` method. To fix this issue, we need to modify the `__init__` method of the `Coder` class to accept the `root` keyword argument and set it as an instance variable
^C KeyboardInterrupt
USER: no, fix the call
ASSISTANT: To fix the call to the `Coder` class in `tests/test_commands.py`, we need to remove the `root` keyword argument and pass the required arguments according to the `__init__` method of the `Coder` class.

Here's the change you need to make in `tests/test_commands.py`:

```python
tests/test_commands.py
<<<<<<< ORIGINAL
            coder = Coder(root=tmpdir)
=======
            coder = Coder(main_model="gpt-3.5-turbo", fnames=[], pretty=False, show_diffs=False, auto_commits=False, io=io, dry_run=False)
>>>>>>> UPDATED
```

This change removes the `root` keyword argument and provides the required arguments for the `Coder` class.

tests/test_commands.py

@@ -10,7 +10,7 @@ class TestCommands(unittest.TestCase):
     def test_cmd_add(self):
         with tempfile.TemporaryDirectory() as tmpdir:
             io = IO(pretty=False, yes=True)
-            coder = Coder(root=tmpdir)
+            coder = Coder(main_model="gpt-3.5-turbo", fnames=[], pretty=False, show_diffs=False, auto_commits=False, io=io, dry_run=False)
             commands = Commands(io, coder)
 
             # Mock the Confirm.ask method to return True for creating files