Fix invalid double-slash comments in main.css

See https://stylelint.io/user-guide/rules/no-invalid-double-slash-comments/

WE2-1296

Signed-off-by: Mart Somermaa <mrts@users.noreply.github.com>

Author: mrts

example/src/main/resources/static/css/main.css

@@ -1,5 +1,5 @@
-// SPDX-FileCopyrightText: Estonian Information System Authority
-// SPDX-License-Identifier: MIT
+/* SPDX-FileCopyrightText: Estonian Information System Authority */
+/* SPDX-License-Identifier: MIT */
 body {
     font-family: "Inv Maison Neue","Maison Neue",-apple-system,BlinkMacSystemFont,"Open Sans",open-sans,sans-serif;
 }