/usr/share/doc/phonon4qt5-backend-gstreamer/changelog.Debian.gz is in phonon4qt5-backend-gstreamer 4:4.9.0-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/phonon4qt5-backend-gstreamer/../phonon-backend-gstreamer-common/changelog.Debian.gz