Fix rubygem-json entry (40194e1c-6d89-11ea-8082-80ee73419af3)

rubygem-json 2.3.0 was erroneously marked as vulnerable.

% cd /usr/ports/devel/rubygem-json
% make fetch

> rubygem-json-2.3.0 has known vulnerabilities:

rubygem-json-2.3.0 is vulnerable:
rubygem-json -- Unsafe Objection Creation Vulnerability in JSON (Additional fix)
CVE: CVE-2020-10663
WWW: https://vuxml.FreeBSD.org/freebsd/40194e1c-6d89-11ea-8082-80ee73419af3.html

1 problem(s) in 1 installed package(s) found.

> Please update your ports tree and try again.

> Note: Vulnerable ports are marked as such even if there is no update available.

> If you wish to ignore this vulnerability rebuild with 'make DISABLE_VULNERABILITIES=yes'

• Error code 1

Stop.
make: stopped in /usr/ports/devel/rubygem-json