ci: [doc] fix url redirect

This solves an URL redirect. (The commit is also used to trigger the test-each-commit CI)

Author: MarcoFalke

.github/workflows/ci.yml

@@ -1,6 +1,6 @@
 # Copyright (c) 2023-present The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
-# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+# file COPYING or https://opensource.org/license/mit.
 
 name: CI
 on: