/usr/share/cups/templates/ca/job-release.tmpl is in cups-server-common 1.7.2-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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<H2 CLASS="title">Allibera la tasca {job_id}</H2>
<P><A HREF="{job_printer_uri}">La tasca {job_id}</A> s'ha alliberat.
</DIV>
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