/usr/share/cups/templates/printer-reject.tmpl is in cups-server-common 2.2.7-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | <H2 CLASS="title">Reject Jobs On {is_class?Class:Printer} {printer_name}</H2>
<P>{is_class?Class:Printer} <A
HREF="/{is_class?classes:printers}/{printer_name}">{printer_name}</A>
is no longer accepting jobs.</P>
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