Update CODE_OF_CONDUCT.md (#1934)
Update CODE_OF_CONDUCT.md (#1934)

Remove Slack from CoC contacts.
redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team,redcanaryco/atomic-red-team