Update ARM Template to support new versions of postgress on azure

### Is your proposal related to a problem?

We are using pg 15 which is available inside docker image of hasura, and we want to make sure the database version are same in production and development

### Describe the solution you'd like
Inside documentation the supported version is 11, I think it should be updated till 15 https://hasura.io/docs/latest/deployment/deployment-guides/azure-container-instances-postgres/

### Describe alternatives you've considered

Tried to edit the ARM Template on portal but deployment failed

Start with the Azure Container Instances Postgres deployment guide linked in the issue and locate the ARM template it describes. Update the supported PostgreSQL version information through 15, then verify that the template and documentation agree and that deployment no longer fails for the requested version.

Written by the indexing model from the issue text.