Inactivity cutoff for retirement from nixpkgs commit bit moving to 6mo

TL;DR: We (@mdaniels5757, @philiptaron, @mattsturgeon) plan to merge nixpkgs-committers#159 one week from now, on or after Thursday, October 30. After that, the retirement automation will flag committers who haven’t merged a PR in six months instead of one year. What’s changing RFC 55 set up retirement of inactive committers, and nixpkgs-committers automates it. Every cutoff that is currently one year becomes six months: Activity: you count as active if you’ve merged a Nixpkgs PR in the last 6...