Drop click handler for changeset entries in the history sidebar

The default click handler in index.js handles them fine, and as this
one was not calling preventDefault both were actually firing in some
browsers, causing the changeset to be loaded twice and two history
entries to be created.

app/assets/javascripts/index/history.js

@@ -8,9 +8,6 @@ OSM.History = function(map) {
     })
     .on("mouseout", "[data-changeset]", function () {
       unHighlightChangeset($(this).data("changeset").id);
-    })
-    .on("click", "[data-changeset]", function () {
-      clickChangeset($(this).data("changeset").id);
     });
 
   var group = L.featureGroup()