Use primary variant for 'New release' button

app/assets/javascripts/releases/components/app_index.vue

@@ -68,7 +68,7 @@ export default {
         :href="newReleasePath"
         :aria-describedby="shouldRenderEmptyState && 'releases-description'"
         category="primary"
-        variant="success"
+        variant="confirm"
         data-testid="new-release-button"
       >
         {{ __('New release') }}