Fix sticky with find as you type

It was losing its position because filtering the list of templates with
find as you type was causing the height of the page to change.

app/assets/javascripts/liveSearch.js

@@ -27,6 +27,12 @@
 
     });
 
+    // make sticky JS recalculate its cache of the element's position
+    // because live search can change the height document
+    if ('stickAtBottomWhenScrolling' in GOVUK) {
+      GOVUK.stickAtBottomWhenScrolling.recalculate();
+    }
+
   };