Add license information to files in matrix-synapse/tasks

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

roles/custom/matrix-synapse/tasks/self_check_client_api.yml

@@ -1,3 +1,10 @@
+# SPDX-FileCopyrightText: 2018 - 2022 Slavi Pantaleev
+# SPDX-FileCopyrightText: 2019 - 2020 Dan Arnfield
+# SPDX-FileCopyrightText: 2020 MDAD project contributors
+# SPDX-FileCopyrightText: 2022 Marko Weltzer
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
 ---
 
 - name: Check Matrix Client API