format_code_in_doc_comments insert extra line with trailing whitespaces if there there's a comment and a hash

[stepancheg]

Input:

//! Test test
//!
//! ```
//! # fn main() {
//! println!("hello"); // Comment
//! # }
//! ```

mod arena;

rustfmt +nightly --config format_code_in_doc_comments=true

outputs:

//! Test test
//!
//! ```
//! # fn main() {
//! println!("hello"); // Comment
//!<5 SPACES>
//! # }
//! ```

mod arena;

rustfmt 1.7.0-nightly (ca663b06 2024-01-08)

[ytmimi]

Thanks for the report. Linking tracking issue for format_code_in_doc_comments #3348