updated icon span with GlLoadingIcon component

app/assets/javascripts/blob/pdf/index.js

 import Vue from 'vue';
 import pdfLab from '../../pdf/index.vue';
+import { GlLoadingIcon } from '@gitlab/ui';
 
 export default () => {
   const el = document.getElementById('js-pdf-viewer');
@@ -8,6 +9,7 @@ export default () => {
     el,
     components: {
       pdfLab,
+      GlLoadingIcon,
     },
     data() {
       return {
@@ -32,11 +34,7 @@ export default () => {
         <div
           class="text-center loading"
           v-if="loading && !error">
-          <span
-            class="spinner spinner-sm"
-            aria-hidden="true"
-            aria-label="PDF loading">
-          </span>
+          <gl-loading-icon />
         </div>
         <pdf-lab
           v-if="!loadError"