az pipelines list with --source-branch comes out empty

- If the issue is to do with Azure CLI 2.0 in-particular, create an issue here at [Azure/azure-cli](https://github.com/Azure/azure-cli/issues)

### Extension name (the extension in question)

azure-devops

```
azure-cli 2.16.0

core 2.16.0
telemetry 1.0.6

Extensions:
azure-devops 0.18.0
```

### Description of issue (in as much detail as possible)

when using something like this

```
az pipelines release list --definition-id=9 --source-branch 'master' -o table
# or
az pipelines release list --definition-id=9 --source-branch 'stable/8.12' -o table
```

The result of the releases always comes empty