Fix missing line comment in doc_markdown example

rustfmt [wrapped the line](b25b6b3355 (diff-561823671726302d969756ded53a13a7L22)), so we need a second `///`

clippy_lints/src/doc.rs

@@ -21,7 +21,7 @@ use url::Url;
 /// **Examples:**
 /// ```rust
 /// /// Do something with the foo_bar parameter. See also
-/// that::other::module::foo.
+/// /// that::other::module::foo.
 /// // ^ `foo_bar` and `that::other::module::foo` should be ticked.
 /// fn doit(foo_bar) { .. }
 /// ```