Azure Synapse Analytics - createManagedPrivateEndpoint feature not idempotent

As @dubansal mentions in [#15602](https://github.com/Azure/azure-rest-api-specs/pull/15602), creating a managed private endpoint on the default storage account of a Synapse workspace is designed only to be executed when first creating the workspace. Without wrapping this property in conditional logic, any repeated use of this API through, say, Azure Bicep will fail, even if the property remains unchanged in subsequent deployments.

A fix for this appears to be the [x-ms-mutability](https://azure.github.io/autorest/extensions/#x-ms-mutability) extension. Currently, the createManagedPrivateEndPoint feature is [set to Create and Update](https://github.com/Azure/azure-rest-api-specs/blob/c707369d97c07867db1331b0c2d1addcdd71f794/specification/synapse/resource-manager/Microsoft.Synapse/stable/2021-06-01/workspace.json). Would setting it to Create and Read be more appropriate?


Start with specification/synapse/resource-manager/Microsoft.Synapse/stable/2021-06-01/workspace.json and inspect the createManagedPrivateEndpoint definition alongside the linked x-ms-mutability guidance. Confirm the appropriate mutability for repeated deployments and validate the specification change with the repository's relevant checks; done means the endpoint behavior is represented correctly in the spec.

Written by the indexing model from the issue text.