.gitlab-ci.yml: remove dco

scripts/check-dco

@@ -1,12 +0,0 @@
-#!/usr/bin/env bash
-
-emails=$(git log master..HEAD --pretty=format:'%ae' | sort | uniq)
-for email in $emails; do
-  printf "checking %s\n" "$email"
-  if ! curl -s 'https://dco.commento.io/api/has-signed' -d "email=$email" -X POST \
-         | jq '.hasSigned' \
-         | grep -q true; then
-    printf "%s has not signed the DCO: https://dco.commento.io\n" "$email"
-    exit 1
-  fi
-done