doc: added missing license header

Signed-off-by: Frederic BIDON <fredbi@yahoo.com>

Author: fredbi

update-fixtures.sh

@@ -1,4 +1,6 @@
-#!/bin/bash 
+#!/bin/bash
+# SPDX-FileCopyrightText: Copyright 2015-2025 go-swagger maintainers
+# SPDX-License-Identifier: Apache-2.0
 
 set -eu -o pipefail
 dir=$(git rev-parse --show-toplevel)