Apply suggestions from code review

Co-authored-by: Yuki Okushi <jtitor@2k36.org>

src/dot-operator.md

@@ -88,7 +88,7 @@ However, `bar_cloned` actually has type `&Container<T>`. Surely this doesn't mak
 sense - we added `#[derive(Clone)]` to `Container`, so it must implement `Clone`!
 Looking closer, the code generated by the `derive` macro is (roughly):
 
-```rust.ignore
+```rust,ignore
 impl<T> Clone for Container<T> where T: Clone {
     fn clone(&self) -> Self {
         Self(Arc::clone(&self.0))