0.8.1 regression - formatter removes strings causing a syntax error on multiline fstring with implicitly concatenated strings and an `if` expression inside it

before:
```py
f"""{'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' 'a' if True else ""}\
a"""
```

after:
```py
f"""{ if True else ""}\
a"""
```

[playground](https://play.ruff.rs/53e2a577-7898-4ac9-9ceb-c5c0c26eca36)