Remove sticky-diff functionality

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/assets/javascripts/merge_request_tabs.js.coffee

@@ -69,7 +69,6 @@ class @MergeRequestTabs
       @loadCommits($target.attr('href'))
     else if action == 'diffs'
       @loadDiff($target.attr('href'))
-      @stickyDiffHeaders()
 
     @setCurrentAction(action)
 
@@ -137,15 +136,11 @@ class @MergeRequestTabs
       url: "#{source}.json"
       success: (data) =>
         document.getElementById('diffs').innerHTML = data.html
-        @stickyDiffHeaders()
         @diffsLoaded = true
 
   toggleLoading: ->
     $('.mr-loading-status .loading').toggle()
 
-  stickyDiffHeaders: ->
-    $('.diff-header').trigger('sticky_kit:recalc')
-
   _get: (options) ->
     defaults = {
       beforeSend: @toggleLoading

app/views/projects/diffs/_diffs.html.haml

@@ -20,6 +20,3 @@
       Failed to collect changes
     %p
       Maybe diff is really big and operation failed with timeout. Try to get diff locally
-
-:coffeescript
-  $('.files .diff-header').stick_in_parent(offset_top: $('.navbar').height())