[analyzer] Fix keyboard navigation for .msgNote events

[george.karpenkov]

Summary

Does not go to msgNote's.

[NoQ]

*is a happy user of the feature*
*appreciates*

lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp

 var numToId = function(num) {
   if (num == 0) {
     return document.getElementById("EndPath")
   }
   return document.getElementById("Path" + num);
 };
 
 var navigateTo = function(up) {
-  var numItems = document.querySelectorAll(".line > .msg").length;
+  var numItems = document.querySelectorAll(
+      ".line > .msgEvent, .line > .msgControl").length;
   var currentSelected = findNum();
   var newSelected = move(currentSelected, up, numItems);
   var newEl = numToId(newSelected, numItems);
 
   // Scroll element into center.
   scrollTo(newEl);
 };