Fix `SIM102` to handle indented `elif` (#6072)
<!--
Thank you for contributing to Ruff! To help us out with reviewing,
please consider the following:
- Does this pull request include a summary of the change? (See below.)
- Does this pull request include a descriptive title?
- Does this pull request include references to any relevant issues?
-->
## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
The `SIM102` auto-fix fails if `elif` is indented like this:
## Example
```python
def f():
# SIM102
if a:
pass
elif b:
if c:
d
```
```
> cargo run -p ruff_cli -- check --select SIM102 --fix a.py
...
error: Failed to fix nested if: Failed to extract statement from source
a.py:5:5: SIM102 Use a single `if` statement instead of nested `if` statements
Found 1 error.
```
## Test Plan
<!-- How was it tested? -->
New test
