Apim Api Revision fails when parent Api has no Description

**Bicep version**
Bicep CLI version 0.25.53

**Describe the bug**
When creating an Apim Api Revision if parent revision e.g. 1 has no Api Description the creation of new Api Revision fails with message:
'....Deployment template validation failed: 'The value for the template parameter 'description' at line...'

**To Reproduce**
1. Create an Api Revision from existing Api without 'Description'

**Additional context**
N/A

Start by reproducing the APIM API Revision scenario with Bicep CLI 0.25.53, using an existing parent API with no Description. Trace the API revision type or template handling in the bicep-types-az repository; done means creating the revision no longer fails with the missing `description` template-parameter validation error.

Written by the indexing model from the issue text.