The 4.2.e uses the new Dojo based header. The share-header.get.js is the file you are looking for. Read up on Dave Drapers blog posts on the subject.
http://blogs.alfresco.com/wp/developer/2013/09/04/customizing-the-share-header-menu-part-1/
All the menu definitions can be found in the file share-header.lib.js
The one you want to hide has the id: HEADER_TASKS.