Update events on swimlanes sidebar epic item

It now used "open" instead of "changed"

ee/app/assets/javascripts/boards/components/sidebar/board_sidebar_epic_select.vue

@@ -41,10 +41,8 @@ export default {
       receiveEpicsSuccess: RECEIVE_EPICS_SUCCESS,
     }),
     ...mapActions(['setActiveIssueEpic']),
-    handleEdit(isEditing) {
-      if (isEditing) {
-        this.$refs.epicSelect.handleEditClick();
-      }
+    openEpicsDropdown() {
+      this.$refs.epicSelect.handleEditClick();
     },
     async setEpic(selectedEpic) {
       this.loading = true;
@@ -80,7 +78,7 @@ export default {
     ref="sidebarItem"
     :title="__('Epic')"
     :loading="loading"
-    @changed="handleEdit"
+    @open="openEpicsDropdown"
   >
     <template v-if="storedEpic.title" #collapsed>
       <a class="gl-text-gray-900! gl-font-weight-bold" href="#">

ee/spec/frontend/boards/components/sidebar/board_sidebar_epic_select_spec.js

@@ -40,6 +40,7 @@ describe('ee/boards/components/sidebar/board_sidebar_epic_select.vue', () => {
   };
 
   const findEpicSelect = () => wrapper.find({ ref: 'epicSelect' });
+  const findItemWrapper = () => wrapper.find({ ref: 'sidebarItem' });
   const findCollapsed = () => wrapper.find('[data-testid="collapsed-content"]');
 
   it('renders "None" when no epic is selected', () => {
@@ -47,6 +48,13 @@ describe('ee/boards/components/sidebar/board_sidebar_epic_select.vue', () => {
     expect(findCollapsed().text()).toBe('None');
   });
 
+  it('expands the dropdown when editing', () => {
+    createWrapper();
+    wrapper.setMethods({ openEpicsDropdown: jest.fn() });
+    findItemWrapper().vm.$emit('open');
+    expect(wrapper.vm.openEpicsDropdown).toHaveBeenCalled();
+  });
+
   describe('when epic is selected', () => {
     beforeEach(async () => {
       createWrapper();