Suggestion of useless_attribute breaks rustfix

[flip1995]

Minimal reproducer:

fn foo() {
    #[allow(clippy::almost_swapped)]
    use std::collections::HashMap;

    let _ = HashMap::default();
}

produces

error: useless lint attribute
 --> src/main.rs:2:1
  |
2 |     #[allow(clippy::almost_swapped)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: if you just forgot a `!`, use: `#![allow(clippy::almost_swapped)]`
  |
  = note: `#[deny(clippy::useless_attribute)]` on by default
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_attribute

The suggestion in itself is correct. This trips rustfix though, since rustfix removes indentations of suggestions and then slices the text pointed at from the suggestion. Relevant rustfix code can be found here: https://github.com/rust-lang/rustfix/blob/715eff0b15b6ffc5adcb016b6713132159681723/src/lib.rs#L95-L113

Playground

[flip1995]

I'll assign this issue to myself. If I shouldn't get to open a PR about this though, it's up for grabs.