Enhance ml vertex ai doc to show how to override the default region

[davidlrosenblum]

Feature description (Mandatory)

Add text to describe where to discover where GCP regions are Add the configuration map that demonstrates the map

Considered alternatives

I considered asking for a code change to remove the default of region.

How this feature can improve the project?

Putting this in will reduce requests such has Why am I running out of quota. How do I change the processing region of the request