Leave `d-flex-center` out of approvals_footer

**Why?**
Even though we technically want this centered, 
for some reason the actual icon isn't quite
centered, so it looks better when left alone.

ee/app/assets/javascripts/vue_merge_request_widget/components/approvals/multiple_rule/approvals_footer.vue

@@ -59,7 +59,7 @@ export default {
   <div>
     <div class="mr-widget-extension d-flex align-items-center pl-3">
       <button
-        class="btn btn-blank square s32 d-flex-center append-right-default"
+        class="btn btn-blank square s32 append-right-default"
         type="button"
         :aria-label="ariaLabel"
         @click="toggle"