format comments bug: comment merges with the next line even if it's a code block opener.

[Lokathor]

A doc comment such as

/// Compute `u8` abs(a - b) then sum eight values at a time into two `u64` lanes.
/// ```

Becomes

/// Compute `u8` abs(a - b) then sum eight values at a time into two `u64`
/// lanes. ```

It should be

/// Compute `u8` abs(a - b) then sum eight values at a time into two `u64`
/// lanes.
/// ```