Remove sign-in token authentication, instead send e-mail about new sign-in (#17970)

app/javascript/styles/mailer.scss

@@ -435,6 +435,10 @@ h5 {
     background: $success-green;
   }
 
+  &.warning-icon td {
+    background: $gold-star;
+  }
+
   &.alert-icon td {
     background: $error-red;
   }