fix copyright statements in templates

because we used the annotate function of reuse, copyright statements have been added as

<--
SPDX-FileCopyrightText: 2020-2023 Helmholtz-Zentrum hereon GmbH

SPDX-License-Identifier: EUPL-1.2
-->

this MR now changes these sections into correct django template syntax, i.e.

{% comment %}
SPDX-FileCopyrightText: 2020-2023 Helmholtz-Zentrum hereon GmbH

SPDX-License-Identifier: EUPL-1.2
{% endcomment %}