www/rubygem-cgi: Update to 0.3.1

Changes: https://github.com/ruby/cgi/commits/v0.3.1
PR: 260034
Approved by: maintainer timeout (> 2 weeks)
Security: CVE-2021-41816
Security: CVE-2021-41819
MFH: 2021Q4

(cherry picked from commit cf62eea7a5fde939ee4961a22155eb476253fea6)