cli: add note to changelog related to amtool update
cli: add note to changelog related to amtool update

Signed-off-by: Paul Gier <02c55f18a892b365bcd1802db9e5c9df39c04674@redhat.com>

prometheus/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager