False positive in doc_markdown unbalanced backticks if code block in list contains backtick

[dtolnay]

//! - ```rust
//!   /// `lol`
//!   pub struct Struct;
//!   ```

fn main() {}

$ cargo clippy --tests -- -Dclippy::pedantic
error: backticks are unbalanced
 --> src/main.rs:1:1
  |
1 | / //! - ```rust
2 | | //!   /// `lol`
  | |_______________^
  |
  = note: `-D clippy::doc-markdown` implied by `-D clippy::pedantic`
  = help: a backtick may be missing a pair
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown

This seems like a false positive. There are no unbalanced backticks in the above.

Mentioning @ebobrow @xFrednet @flip1995 who touched this lint in #7357.

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• cargo clippy -V: clippy 0.1.55 (798baeb 2021-07-02)
• rustc -Vv:

  rustc 1.55.0-nightly (798baebde 2021-07-02)
  binary: rustc
  commit-hash: 798baebde1fe77e5a660490ec64e727a5d79970d
  commit-date: 2021-07-02
  host: x86_64-unknown-linux-gnu
  release: 1.55.0-nightly
  LLVM version: 12.0.1