dotfiles expired signature during new user onboarding

[ValdikSS]

Submodule path 'zsh/.grml-etc-core': checked out 'c5383b10d449697922b6da3262b63a95ed5cc83d'
gpg: keybox '/tmp/gpg.Qb67Yi/pubring.kbx' created
gpg: Signature made Sun 01 Sep 2019 05:29:47 AM UTC
gpg:                using RSA key 81B0924EBE376FE63B5EEEBF4E0AF802FFF7960C
gpg: Good signature from "Ben Harris <ben@tilde.team>" [expired]
gpg:                 aka "Ben Harris <benharri@hashbang.sh>" [expired]
gpg: WARNING: Using untrusted key!
CRITICAL: Failed to verify signature on dotfiles