x11/libXxf86vm: update to 1.1.5

Remove GNU_CONFIGURE_MANPREFIX

Changes: https://gitlab.freedesktop.org/xorg/lib/libxxf86vm/-/compare/libXxf86vm-1.1.4...libXxf86vm-1.1.5
Reviewed by: diizzy, jbeich
Tested by: arrowd
Pull Request: https://github.com/freebsd/freebsd-ports/pull/273
Sponsored by: Serenity Cybersecurity, LLC