Design tweaks to str bar

src/sentry/static/sentry/less/auth.less

@@ -331,7 +331,11 @@ div.u2f-box {
   &.visible {
     display: block;
   }
+  .progress {
+    margin: 5px 0;
+  }
   .progress-bar {
+    border-radius: 2px;
     height: 14px;
   }
 }