Update docs/configuring-playbook-jitsi.md: add the copyright header

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

docs/configuring-playbook-jitsi.md

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+SPDX-FileCopyrightText: 2020 - 2024 Slavi Pantaleev
+SPDX-FileCopyrightText: 2020 - 2024 MDAD project contributors
+SPDX-FileCopyrightText: 2020 Aaron Raimist
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+SPDX-FileCopyrightText: 2023 Antonis Christofides
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 # Setting up the Jitsi video-conferencing platform (optional)
 
 The playbook can install and configure the [Jitsi](https://jitsi.org/) video-conferencing platform for you.