Update net-p2p/qbittorrent to 3.3.16

• remove INSTALLS_ICONS as this is not a gnome port.
• while here, switch to DISTVERSION

PR: 223113
Submitted by: Ralf van der Enden <tremere@cainites.net>
Approved by: Yuri Victorovich <yuri@rawbw.com> (maintainer)