Strip last backline from non-rust code examples

Author: GuillaumeGomez

Diff for: src/librustdoc/html/markdown.rs

@@ -261,7 +261,9 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
                                  </pre>\
                              </div>",
                                 added_classes = added_classes.join(" "),
-                                text = Escape(&original_text),
+                                text = Escape(
+                                    original_text.strip_suffix('\n').unwrap_or(&original_text)
+                                ),
                             )
                             .into(),
                         ));