net/freerdp3: update to 3.1.0

Changelogs:
https://github.com/FreeRDP/FreeRDP/releases/tag/3.1.0
https://github.com/FreeRDP/FreeRDP/releases/tag/3.0.0
https://github.com/FreeRDP/FreeRDP/releases/tag/3.0.0-rc0
https://github.com/FreeRDP/FreeRDP/releases/tag/3.0.0-beta4
https://github.com/FreeRDP/FreeRDP/releases/tag/3.0.0-beta3
https://github.com/FreeRDP/FreeRDP/releases/tag/3.0.0-beta2
https://github.com/FreeRDP/FreeRDP/releases/tag/3.0.0-beta1

All FreeRDP consumers in ports doesn't support FreeRDP 3.x yet:
multimedia/vlc, net/gnome-connections, net/guacamole-server, net/krdc,
net/remmina, net/remotebox, net/vinagre.
When support appears, then will rename this port.

Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D43127