net/tightvnc: Deprecate and set expiration date to 2023-03-31

• Last release in 2009 [1]
• New version 2.x is available for Windows only [2]
• Multiple security vulnerabilities are reported and not yet fixed (CVE-2019-15678, CVE-2019-15679, CVE-2019-15680)

[1] https://lwn.net/Articles/322943/
[2] https://www.tightvnc.com/release-2.0.php