docs: Fix subscription expiration ttl documentation (#2149)
docs: Fix subscription expiration ttl documentation (#2149)


jdpedrie/google-cloud-php,googleapis/google-cloud-php,jdpedrie/google-cloud-php,chingor13/google-cloud-php,googleapis/google-cloud-php,googleapis/google-cloud-php,chingor13/google-cloud-php,chingor13/google-cloud-php,jdpedrie/google-cloud-php