/etc/apparmor.d/abstractions/ruby is in apparmor 2.7.102-0ubuntu3.
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 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | # ------------------------------------------------------------------
#
#    Copyright (C) 2002-2006 Novell/SUSE
#    Copyright (C) 2009 Canonical Ltd.
#
#    This program is free software; you can redistribute it and/or
#    modify it under the terms of version 2 of the GNU General Public
#    License published by the Free Software Foundation.
#
# ------------------------------------------------------------------
  /usr/lib{,32,64}/ruby/1.[89]/ r,
  /usr/lib{,32,64}/ruby/1.[89]/*.rb r,
  /usr/lib{,32,64}/ruby/1.[89]/**/*.rb r,
  /usr/lib{,32,64}/ruby/1.[89]/*-linux/*.so mr,
  /usr/lib{,32,64}/ruby/1.[89]/*-linux/**/*.so mr,
  /usr/lib{,32,64}/ruby/site_ruby/1.[89]/ r,
  /usr/lib{,32,64}/ruby/site_ruby/1.[89]/*.rb r,
  /usr/lib{,32,64}/ruby/site_ruby/1.[89]/**/*.rb r,
  /usr/lib{,32,64}/ruby/site_ruby/1.[89]/*-linux/*.so mr,
  /usr/lib{,32,64}/ruby/site_ruby/1.[89]/*-linux/**/*.so mr,
  /usr/lib/ruby/gems/1.[89]/ r,
  /usr/lib/ruby/gems/1.[89]/** r,
 |