Add an example of adding constraints for multiple regions to the Configure Replication Zones page

[rkruze]

Add an example of having multiple constraints for multiple regions

Description

Currently today the only example of an array I could find on the page is the following:
constraints = '[+ssd, -region=west]' I think it would be great to perhaps show something like:

constraints = '[+region=west, +region=central]' to make it clear how this could be used. Showing this in an alter statement down the page would also be great.

Expected Audience

Users who are looking to work with zone constraints.

[jseldess]

Closing in favor of #4459.