Documentation for pagerduty watcher action needs updating re PagerDuty Events API v2

[sparrowt]

Elasticsearch Version

7.17.1

Installed Plugins

No response

Java Version

bundled

OS Version

Cloud hosted linux but N/A as bug is documentation only

Problem Description

The documentation for the "Watcher PagerDuty action" says:

The service must use the API integration.

However on PagerDuty there is no longer any integration called simply "API", but rather various including "Events API v1" and "Events API v2".

It took me a long time to figure out which one was actually being used, especially because many of the attributes for the pagerduty watcher action have names which still match the PagerDuty Events API v1 (which Elastic originally used) even though Elastic now translates these and uses the PagerDuty Events API v2 behind the scenes (since #32285).

Steps to Reproduce

Visit the documentation here and try to follow it:
https://www.elastic.co/guide/en/elasticsearch/reference/master/actions-pagerduty.html

We should update the content, and also ideally backport that to e.g:
https://www.elastic.co/guide/en/elasticsearch/reference/8.4/actions-pagerduty.html
https://www.elastic.co/guide/en/elasticsearch/reference/7.17/actions-pagerduty.html

Logs (if relevant)

No response

[sparrowt]

I've opened #90800 and (hopefully successfully!) signed the CLA.

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Pinging @elastic/es-docs (Team:Docs)

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Pinging @elastic/es-data-management (Team:Data Management)