/usr/share/seccomp/templates/ubuntu-core/16.04/unconfined is in ubuntu-core-security-seccomp 16.04.15.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | # Description: Allows unrestricted access to the system
# Usage: reserved
@unrestricted
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