Rollup merge of rust-lang#49429 - GuillaumeGomez:fix-collapse-toggle-insertion, r=QuietMisdreavus

Fix collapse toggle insertions on impl with docs

Just went through this one randomly... When an impl has docs, the collapse toggle isn't generated. This fixes it.

r? @QuietMisdreavus

Author: kennytm

src/librustdoc/html/static/main.js

@@ -1820,6 +1820,9 @@
 
     var func = function(e) {
         var next = e.nextElementSibling;
+        if (hasClass(e, 'impl') && next && hasClass(next, 'docblock')) {
+            next = next.nextElementSibling;
+        }
         if (!next) {
             return;
         }