/usr/lib/tmpfiles.d/apt-cacher-ng.conf is in apt-cacher-ng 0.9.1-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | Z /run/apt-cacher-ng 0755 apt-cacher-ng apt-cacher-ng - -
D /run/apt-cacher-ng 0755 apt-cacher-ng apt-cacher-ng - -
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