SIM115 open() inside a return statement not reported

### Summary

SIM115 fails to detect open() when it appears inside a return statement:

```
def not_detected():
return [x for x in open("a")]
```

```
def detected():
result = [x for x in open("a")]
```

### Version

ruff 0.15.17

Start by running Ruff against the two Python examples and locating the SIM115 rule implementation and its existing tests. Add a regression case for the list comprehension inside a return statement, then verify that both examples are handled consistently without changing the existing detection behavior.

Written by the indexing model from the issue text.