Track fix isolation in `unnecessary-pass` (#7715)
## Summary
This wasn't necessary in the past, since we _only_ applied this rule to
bodies that contained two statements, one of which was a `pass`. Now
that it applies to any `pass` in a block with multiple statements, we
can run into situations in which we remove both passes, and so need to
apply the fixes in isolation.
See:
https://github.com/astral-sh/ruff/issues/7455#issuecomment-1741107573.
