'ServicePrincipalCredential' is not defined in 1.7.1 connectedk8s

### Describe the bug

After updating to 1.7.1 release of connectedk8s extension, when logged in to a service principal, I am now getting the error message:
Failed to post access token to client proxyname 'ServicePrincipalCredential' is not defined

### Related command

az connectedk8s proxy --name devcluster --resource-group rg-aio050624190206 --port 8001

### Errors

Failed to post access token to client proxyname 'ServicePrincipalCredential' is not defined

### Issue script & Debug output

cli.azure.cli.core.azclierror: Traceback (most recent call last):
File "/home/vscode/.azure/cliextensions/connectedk8s/azext_connectedk8s/_clientproxyutils.py", line 99, in fetch_and_post_at_to_csp
if isinstance(credential._credential, ServicePrincipalCredential):
^^^^^^^^^^^^^^^^^^^^^^^^^^
NameError: name 'ServicePrincipalCredential' is not defined

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/opt/az/lib/python3.11/site-packages/knack/cli.py", line 233, in invoke
cmd_result = self.invocation.execute(args)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/az/lib/python3.11/site-packages/azure/cli/core/commands/__init__.py", line 664, in execute
raise ex
File "/opt/az/lib/python3.11/site-packages/azure/cli/core/commands/__init__.py", line 731, in _run_jobs_serially
results.append(self._run_job(expanded_arg, cmd_copy))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/az/lib/python3.11/site-packages/azure/cli/core/commands/__init__.py", line 701, in _run_job
result = cmd_copy(params)
^^^^^^^^^^^^^^^^
File "/opt/az/lib/python3.11/site-packages/azure/cli/core/commands/__init__.py", line 334, in __call__
return self.handler(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/az/lib/python3.11/site-packages/azure/cli/core/commands/command_operation.py", line 121, in handler
return op(**command_args)
^^^^^^^^^^^^^^^^^^
File "/home/vscode/.azure/cliextensions/connectedk8s/azext_connectedk8s/custom.py", line 2183, in client_side_proxy_wrapper
client_side_proxy_main(cmd, tenant_id, client, resource_group_name, cluster_name, 0, args, client_proxy_port, api_server_port,
File "/home/vscode/.azure/cliextensions/connectedk8s/azext_connectedk8s/custom.py", line 2220, in client_side_proxy_main
expiry, clientproxy_process = client_side_proxy(cmd, tenant_id, client, resource_group_name, cluster_name, 0, args, client_proxy_port,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/vscode/.azure/cliextensions/connectedk8s/azext_connectedk8s/custom.py", line 2308, in client_side_proxy
post_at_response = clientproxyutils.fetch_and_post_at_to_csp(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/vscode/.azure/cliextensions/connectedk8s/azext_connectedk8s/_clientproxyutils.py", line 107, in fetch_and_post_at_to_csp
close_subprocess_and_raise_cli_error(clientproxy_process,
File "/home/vscode/.azure/cliextensions/connectedk8s/azext_connectedk8s/_clientproxyutils.py", line 41, in close_subprocess_and_raise_cli_error
raise CLIInternalError(msg)
azure.cli.core.azclierror.CLIInternalError: Failed to post access token to client proxyname 'ServicePrincipalCredential' is not defined

cli.azure.cli.core.azclierror: Failed to post access token to client proxyname 'ServicePrincipalCredential' is not defined
az_command_data_logger: Failed to post access token to client proxyname 'ServicePrincipalCredential' is not defined

### Expected behavior

logged in with service principal

### Environment Summary

{
"azure-cli": "2.60.0",
"azure-cli-core": "2.60.0",
"azure-cli-telemetry": "1.1.0",
"extensions": {
"azure-iot-ops": "0.5.0b1",
"connectedk8s": "1.7.1",
"k8s-extension": "1.6.1"
}
}

### Additional context

Reverting back to 1.7.0 connectedk8s extension fixes it.

_No response_