aider: Use the released field directly in the plot instead of parsing it with datetime.strptime.

# Aider chat conversation:

USER: I ran this command:

 python benchmark/over_time.py

And got this output:

Traceback (most recent call last):
  File "/Users/gauthier/Projects/aider/benchmark/over_time.py", line 33, in <module>
    plot_over_time('_data/edit_leaderboard.yml')
  File "/Users/gauthier/Projects/aider/benchmark/over_time.py", line 15, in plot_over_time
    dates.append(datetime.strptime(entry['released'], '%Y-%m-%d'))
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: strptime() argument 1 must be str, not datetime.date

ASSISTANT: The error indicates that the `released` field in the YAML file is already a `datetime.date` object, so we don't need to parse it with `datetime.strptime`. We can directly use it in the plot.

Here are the changes:

benchmark/over_time.py
```python
<<<<<<< SEARCH
            dates.append(datetime.strptime(entry['released'], '%Y-%m-%d'))
=======
            dates.append(entry['released'])
>>>>>>> REPLACE
```

benchmark/over_time.py

@@ -12,7 +12,7 @@ def plot_over_time(yaml_file):
 
     for entry in data:
         if 'released' in entry and 'pass_rate_2' in entry:
-            dates.append(datetime.strptime(entry['released'], '%Y-%m-%d'))
+            dates.append(entry['released'])
             pass_rates.append(entry['pass_rate_2'])
             models.append(entry['model'])