net/libvncserver: Enable GCRYPT by default

Currently, the GCRYPT option is not enabled by default in this port.
This prevents libvncclient from connecting to macOS's VNC server.
Also see https://bugs.mageia.org/show_bug.cgi?id=18895

PR: 228113
Submitted by: Greg V <greg@unrelenting.technology>
Approved by: araujo (maintainer timeout, 10 months)