Fix contribution section aligment

app/views/shared/issuable/form/_contribution.html.haml

@@ -7,11 +7,11 @@
 
 %hr
 
-.form-group
-  .col-form-label
+.form-group.row
+  %label.col-form-label.col-sm-2
     = _('Contribution')
   .col-sm-10
-    .form-check
+    .form-check.prepend-top-5
       = form.check_box :allow_collaboration, disabled: !issuable.can_allow_collaboration?(current_user), class: 'form-check-input'
       = form.label :allow_collaboration, class: 'form-check-label' do
         = _('Allow commits from members who can merge to the target branch.')