Polish UI of epic roadmap view

- Update button to use confirm variant instead of success.
- Add missing bottom margin of loading icon.

Changelog: changed
EE: true

ee/app/assets/javascripts/roadmap/components/epics_list_empty.vue

@@ -144,7 +144,7 @@ export default {
           <gl-button
             v-if="!hasFiltersApplied"
             :href="newEpicPath"
-            variant="success"
+            variant="confirm"
             class="gl-mt-3 gl-sm-mt-0! gl-w-full gl-sm-w-auto!"
             data-testid="new-epic-button"
           >

ee/app/assets/javascripts/roadmap/components/roadmap_app.vue

@@ -74,7 +74,7 @@ export default {
   <div class="roadmap-app-container gl-h-full">
     <roadmap-filters v-if="showFilteredSearchbar && !epicIid" @toggleSettings="toggleSettings" />
     <div :class="{ 'overflow-reset': epicsFetchResultEmpty }" class="roadmap-container gl-relative">
-      <gl-loading-icon v-if="epicsFetchInProgress" class="gl-mt-5" size="md" />
+      <gl-loading-icon v-if="epicsFetchInProgress" class="gl-my-5" size="md" />
       <epics-list-empty
         v-else-if="epicsFetchResultEmpty"
         :preset-type="presetType"

ee/spec/frontend/roadmap/components/epics_list_empty_spec.js

@@ -56,7 +56,6 @@ describe('ee/roadmap/components/epics_list_empty.vue', () => {
 
   afterEach(() => {
     wrapper.destroy();
-    wrapper = null;
   });
 
   const findTitle = () => wrapper.findByTestId('title');

ee/spec/frontend/roadmap/components/roadmap_app_spec.js

@@ -52,6 +52,10 @@ describe('RoadmapApp', () => {
   };
 
   const findSettingsSidebar = () => wrapper.findByTestId('roadmap-settings');
+  const findEpicsListEmpty = () => wrapper.findComponent(EpicsListEmpty);
+  const findGlLoadingIcon = () => wrapper.findComponent(GlLoadingIcon);
+  const findRoadmapFilters = () => wrapper.findComponent(RoadmapFilters);
+  const findRoadmapShell = () => wrapper.findComponent(RoadmapShell);
 
   beforeEach(() => {
     store = createStore();
@@ -87,15 +91,15 @@ describe('RoadmapApp', () => {
       });
 
       it(`loading icon is${showLoading ? '' : ' not'} shown`, () => {
-        expect(wrapper.find(GlLoadingIcon).exists()).toBe(showLoading);
+        expect(findGlLoadingIcon().exists()).toBe(showLoading);
       });
 
       it(`roadmap is${showRoadmapShell ? '' : ' not'} shown`, () => {
-        expect(wrapper.find(RoadmapShell).exists()).toBe(showRoadmapShell);
+        expect(findRoadmapShell().exists()).toBe(showRoadmapShell);
       });
 
       it(`empty state view is${showEpicsListEmpty ? '' : ' not'} shown`, () => {
-        expect(wrapper.find(EpicsListEmpty).exists()).toBe(showEpicsListEmpty);
+        expect(findEpicsListEmpty().exists()).toBe(showEpicsListEmpty);
       });
     },
   );
@@ -107,7 +111,7 @@ describe('RoadmapApp', () => {
     });
 
     it('shows epic-list-empty component', () => {
-      const epicsListEmpty = wrapper.findComponent(EpicsListEmpty);
+      const epicsListEmpty = findEpicsListEmpty();
       expect(epicsListEmpty.exists()).toBe(true);
       expect(epicsListEmpty.props()).toMatchObject({
         emptyStateIllustrationPath,
@@ -133,17 +137,17 @@ describe('RoadmapApp', () => {
 
       await nextTick();
 
-      expect(wrapper.findComponent(RoadmapFilters).exists()).toBe(false);
+      expect(findRoadmapFilters().exists()).toBe(false);
     });
 
     it('shows roadmap filters UI when epicIid is not present', () => {
       // By default, `epicIid` is not set on store.
-      expect(wrapper.findComponent(RoadmapFilters).exists()).toBe(true);
+      expect(findRoadmapFilters().exists()).toBe(true);
     });
 
     it('shows roadmap-shell component', () => {
-      const roadmapShell = wrapper.findComponent(RoadmapShell);
-      expect(wrapper.find(RoadmapShell).exists()).toBe(true);
+      const roadmapShell = findRoadmapShell();
+      expect(roadmapShell.exists()).toBe(true);
       expect(roadmapShell.props()).toMatchObject({
         currentGroupId,
         epics,