fix closing tags of async_button component

app/assets/javascripts/vue_pipelines_index/components/async_button.vue

@@ -88,8 +88,9 @@ export default {
     :aria-label="title"
     data-container="body"
     data-placement="top"
-    :disabled="isLoading">
-    <i :class="iconClass" aria-hidden="true"/>
-    <i class="fa fa-spinner fa-spin" aria-hidden="true" v-if="isLoading"
-  />
+    :disabled="isLoading"
+  >
+    <i :class="iconClass" aria-hidden="true"></i>
+    <i class="fa fa-spinner fa-spin" aria-hidden="true" v-if="isLoading"></i>
+  </button>
 </template>