## Summary
This PR add the `fix safety` section for rule `B006` in
`mutable_argument_default.rs` for #15584
When applying this rule for fixes, certain changes may alter the
original logical behavior. For example:
before:
```python
def cache(x, storage=[]):
storage.append(x)
return storage
print(cache(1)) # [1]
print(cache(2)) # [1, 2]
```
after:
```python
def cache(x, storage=[]):
storage.append(x)
return storage
print(cache(1)) # [1]
print(cache(2)) # [2]
```
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