Update PagerDuty doc links (#2314)
Update PagerDuty doc links (#2314)

PagerDuty has restructured their documentation, making links stale

Signed-off-by: Calle Pettersson <8f9f97eb45ed102f8faf72e01bebf7b2c1679978@cape.nu>
prometheus/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager