/usr/lib/x86_64-linux-gnu/libQtAssistantClient.so.4.7 is in libqtassistantclient4 4.6.3-3ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libQtAssistantClient.so.4.7.4