Filter out empty lines after hidden lines in Rust codeblocks

[zjp-CN]

Current in term-rustdoc

Same as the HTML on https://docs.rs/actix/0.13.0/actix/sync/struct.SyncContext.html

/// ```
/// use actix::prelude::*;
///
/// # struct Fibonacci(pub u32);
///
/// # impl Message for Fibonacci {
/// #     type Result = Result<u64, ()>;
/// # }
///
/// struct SyncActor;
///
/// impl Actor for SyncActor {
///     // It's important to note that you use "SyncContext" here instead of "Context".
///     type Context = SyncContext<Self>;
/// }
///
/// # fn main() {
/// # }
/// ```