az devops security permission update --namespace-id 2e9eb7ed-3c0a-47d4-87c1-0ffdd275fd87 fails with ClientRequestError

### **This is autogenerated. Please review and update as needed.**

## Describe the bug

**Command Name**
`az devops security permission update
Extension Name: azure-devops. Version: 0.18.0.`

**Errors:**
```
ClientRequestError: Error occurred in request., RetryError: HTTPSConnectionPool(host='dev.azure.com', port=443): Max retries exceeded with url: /rainer0000/_apis/AccessControlEntries/2e9eb7ed-3c0a-47d4-87c1-0ffdd275fd87 (Caused by ResponseError('too many 500 error responses',))
```

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

- _Put any pre-requisite steps here..._
- `az devops security permission update --allow-bit 1 --namespace-id 2e9eb7ed-3c0a-47d4-87c1-0ffdd275fd87 --subject 'vssgp.Uy0xLTktMTU1MTM3NDI0NS0xODM1NDM5NDMzLTM0OTczMTQ4ODEtMjE1OTA1MTMxNy0zNjc1NDExMzMwLTEtMjc0NTczOTUxxxxxxxxxxxxxxxxi0xMzEyMDY4MDU' --token 'repoV2/MyProject'`

## Expected Behavior
Permission is updated

## Environment Summary
```
Windows-10-10.0.19041-SP0
Python 3.6.8
Installer: MSI

azure-cli 2.14.0 *

Extensions:
azure-devops 0.18.0

```
## Additional Context
tried with different subject as well (descriptor id, display name)