fix(css): make qr code padding consistent (#6048), r=@shane-tomlinson

app/styles/modules/_settings-totp.scss

@@ -80,8 +80,7 @@
   .totp-details {
     .qr-image-container {
       height: 228px;
-      margin: auto;
-      padding-bottom: 10px;
+      margin: auto auto 24px auto;
       width: 228px;
     }