Update ECS Postgres Agent integration Docs to include AutoDiscovery v2 Checks

[colinbjohnson]

Autodiscovery Configuration for the Postgres integration should should cover AutoDiscovery configuration for latest DataDog Agent versions or all configurations.

Desired configuration: describe postgres ECS configuration using AD Annotations v2 usingagent 7.36.1 or newer (release date May 31, 2022, https://github.com/DataDog/datadog-agent/releases/tag/7.36.1) or cover both AD Annotations v2 and AD Annotations v1.

Existing configuration: describes ECS configuration using configuring AD Annotations v1 only.

I have submitted a PR for this here: #19925