Fix `empty_line_after_outer_attribute` false positive
This PR fixes a false positive in `empty_line_after_outer_attribute`.
Here is a minimal example that trigger the FP:
```rust
#[derive(clap::Parser)]
#[clap(after_help = "This ia a help message.
You're welcome.
")]
pub struct Args;
```
changelog: PF: [`empty_line_after_outer_attribute`]: No longer lints empty lines in inner string values.
1dd55471b4