lang/ruby26: Update to 2.6.9

While here, mark DEPRECATED and set EXPIRATION_DATE.

RelaseNotes: https://www.ruby-lang.org/en/news/2021/11/24/ruby-2-6-9-released/
PR: 260026
Approved by: maintainer timeout (> 2 weeks)
Security: CVE-2021-41817
Security: CVE-2021-41819
MFH: 2021Q4