Hide whitespace toggle button for new merge requests

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

+- show_whitespace_toggle = local_assigns.fetch :show_whitespace_toggle, true
 - if diff_view == 'parallel'
   - fluid_layout true
 
@@ -5,6 +6,7 @@
 
 .content-block.oneline-block.files-changed
   .inline-parallel-buttons
+    - if show_whitespace_toggle
       - if current_controller?(:commit)
         = commit_diff_whitespace_link(@project, @commit)
       - if current_controller?(:merge_requests)

app/views/projects/merge_requests/_new_submit.html.haml

@@ -42,7 +42,7 @@
           %h4 This comparison includes more than #{MergeRequestDiff::COMMITS_SAFE_SIZE} commits.
           %p To preserve performance the line changes are not shown.
       - else
-        = render "projects/diffs/diffs", diffs: @diffs, project: @project, diff_refs: @merge_request.diff_refs
+        = render "projects/diffs/diffs", diffs: @diffs, project: @project, diff_refs: @merge_request.diff_refs, show_whitespace_toggle: false
     - if @ci_commit
       #builds.builds.tab-pane
         = render "projects/merge_requests/show/builds"