aider: Added display_fname arg to quoted_file and updated call to quoted_file to pass relative file path.

# Context:
USER: add a display_fname arg to quoted_file. add it, not fname, into the prompt. change the call to quoted_file to pass along the fname relative to self.root
ASSISTANT: To add a `display_fname` argument to the `quoted_file` function and update the call to `quoted_file`, follow these changes:

1. Add the `display_fname` argument to the `quoted_file` function definition.
2. Replace `fname` with `display_fname` in the prompt string.
3. Update the call to `quoted_file` in the `get_files_content` method to pass the relative file path.

Here are the code changes:

```python
aider/utils.py
<<<<<<< ORIGINAL
def quoted_file(fname):
    prompt = "\n"
    prompt += fname
=======
def quoted_file(fname, display_fname):
    prompt = "\n"
    prompt += display_fname
>>>>>>> UPDATED
    prompt += "\n```\n"
    prompt += Path(fname).read_text()
    prompt += "\n```\n"
    return prompt
```

```python
aider/coder.py
<<<<<<< ORIGINAL
        for fname in self.fnames:
            prompt += utils.quoted_file(fname)
=======
        for fname in self.fnames:
            relative_fname = os.path.relpath(fname, self.root)
            prompt += utils.quoted_file(fname, relative_fname)
>>>>>>> UPDATED
        return prompt
```

aider/coder.py

@@ -132,7 +132,8 @@ class Coder:
     def get_files_content(self):
         prompt = ""
         for fname in self.fnames:
-            prompt += utils.quoted_file(fname)
+            relative_fname = os.path.relpath(fname, self.root)
+            prompt += utils.quoted_file(fname, relative_fname)
         return prompt
 
     def get_last_modified(self):