now-certs: Fix typo on formatExpirationDate()
now-certs: Fix typo on formatExpirationDate()

zeit/now-cli,zeit/now-cli,zeit/now-cli,mike-engel/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli,southpolesteve/now-cli,zeit/now-cli,southpolesteve/now-cli