All available extensions denoted as non-experimental

### Describe the bug

The `az extension list-available` command denotes every extension as non-experimental.

---
Using the `cli-translator` extension as an example:

- Denoted as experimental in [azext_metadata.json](https://github.com/Azure/azure-cli-extensions/blob/11b77782dc4014f449cbc4411473baa65ac0ded5/src/cli-translator/azext_cli_translator/azext_metadata.json#L2).
- Denoted as experimental in the [available extensions documentation](https://learn.microsoft.com/en-us/cli/azure/azure-cli-extensions-list).

- Denoted as non-experimental in the `extension list-available` results.

### Related command

`az extension list-available`

### Errors

N/A

### Issue script & Debug output

N/A

### Expected behavior

Experimental extensions have the `experimental` property set to `true` in the command output.

### Environment Summary

azure-cli 2.83.0

core 2.83.0
telemetry 1.1.0

Dependencies:
msal 1.35.0b1
azure-mgmt-resource 23.3.0

Python location 'C:\Program Files\Microsoft SDKs\Azure\CLI2\python.exe'
Config directory 'C:\Users\lancra\.azure'
Extensions directory 'C:\Users\lancra\.azure\cliextensions'

Python (Windows) 3.13.11 (tags/v3.13.11:6278944, Dec 5 2025, 16:26:58) [MSC v.1944 64 bit (AMD64)]

### Additional context

_No response_