/usr/share/igtf-policy/classic/DigiCertAssuredIDRootCA-Root.namespaces is in igtf-policy-classic 1.59-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#NAMESPACES-VERSION: 1.0
#
# @(#)69105f4f.namespaces
# CA alias    : DigiCertAssuredIDRootCA-Root
#    subord_of: 
#    subjectDN: /C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert Assured ID Root CA
#    hash     : 69105f4f
#    (generated automatically from 69105f4f.signing_policy)
#
TO Issuer "/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert Assured ID Root CA" \
  PERMIT Subject "/C=US/O=DigiCert Grid/OU=www.digicert.com/CN=DigiCert Grid Trust CA"
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