Fix DBForPostgresSQL pipeline

[eriqua]

Deployment validation failing for 2/3 module tests:

Private is failing due to

'Failed'.",     "details": [       {         "code":
       | "PrivateDnsZoneHasWrongZoneSuffix",         "message": "The
       | Private DNS Zone name provided is not valid. It has to end
       | with .postgres.database.azure.com."       }     ]

Public is failing due to generic conflict.

[AlexanderSehr]

It appears this is a special case for this resource provider. When comparing the parameter files it becomes relatively apparant ...