This issue is a: (mark with an x)

• bug report -> please search issues before submitting
• documentation issue or request
• regression (a behavior that used to work and stopped in a new release)

Issue description

In Azue CLI containerapp extension v0.3.6, I ran to change the authentication to ACR to a Managed ID using az containerapp registry set --identity command, but the username and passwordSecretRef settings are still remain.

Steps to reproduct

1. The following command was executed for existing ACA (deploy from ACR, authentication method is username/password).

az containerapp registry set \
  -n '<ACA Name>' \
  -g '<Resouce Group Name>' \
  --server '<ACR Server Name>' \
  --identity 'system'

Expected behavior [What you expected to happen.]
I think the execution result should be like this.

Updating existing registry.
[
  {
    "identity": "system",
    "server": "<ACR Server Name>",
  }
]

Actual behavior [What actually happened.]
Actually, the result is as follows.
Note : The result was the same for --identity '<user-assigned managed ID'

Updating existing registry.
[
  {
    "identity": "system",
    "passwordSecretRef": "<Password (Secret)>",
    "server": "<ACR Server Name>",
    "username": "<User Name>"
  }
]

Additional context

• az version resuilts

{
  "azure-cli": "2.37.0",
  "azure-cli-core": "2.37.0",
  "azure-cli-telemetry": "1.0.6",
  "extensions": {
    "containerapp": "0.3.6",
    "ssh": "1.1.1"
  }
}