Don't show due date in red on epic related issues if issue is closed

Issues shown in the epic related items tree have a due shown in red
even when the issue is closed. This is because the closed state was
not provided to the item-due-date component.

Changelog: changed

ee/app/assets/javascripts/related_items_tree/components/tree_item_body.vue

@@ -254,6 +254,7 @@ export default {
             <item-due-date
               v-if="item.dueDate"
               :date="item.dueDate"
+              :closed="Boolean(item.closedAt)"
               tooltip-placement="top"
               css-class="item-due-date gl-display-flex gl-align-items-center gl-mr-5!"
             />

ee/spec/frontend/related_items_tree/components/tree_item_body_spec.js

@@ -361,6 +361,19 @@ describe('RelatedItemsTree', () => {
         expect(dueDate.isVisible()).toBe(true);
       });
 
+      it('does not render red icon for overdue issue that is closed', async () => {
+        wrapper.setProps({
+          item: {
+            ...mockItem,
+            closedAt: '2018-12-01T00:00:00.00Z',
+          },
+        });
+
+        await wrapper.vm.$nextTick();
+
+        expect(wrapper.find(ItemDueDate).props('closed')).toBe(true);
+      });
+
       it('renders item weight when it has weight', () => {
         const weight = wrapper.find(ItemWeight);