Newline removed with --verus-only

With `--verus-only` set, verusfmt still removes a newline from a file with no verus! macro. 
```rust
// The newline below this comment is deleted with --verus-only.

use std::marker::PhantomData;

pub fn main(){ } // Formatting error here pops up without --verus-only

```

Test here: https://github.com/rsofaer/verusfmt/commit/2487fd686b211b054b784fd8fc673f07b71ab7ec