[Bug]: Incorrect label count in prometheus metrics reporting

[micahjsmith]

What happened?

Seeing an error in async callback deading with prometheus label count. This does not cause any completion requests to fail, but errors like this make me worried that prometheus metrics are not accurate representation of system health and performance. This is a regression as in v1.54.1 this error was not present.

Relevant log output

Task exception was never retrieved
future: <Task finished name='Task-769554' coro=<ServiceLogging.async_service_failure_hook() done, defined at /usr/local/lib/python3.13/site-packages/litellm/_service_logger.py:207> exception=ValueError('Incorrect label count')>
Traceback (most recent call last):
  File "/usr/local/lib/python3.13/site-packages/litellm/_service_logger.py", line 243, in async_service_failure_hook
    await self.prometheusServicesLogger.async_service_failure_hook(
    ...<2 lines>...
    )
  File "/usr/local/lib/python3.13/site-packages/litellm/integrations/prometheus_services.py", line 207, in async_service_failure_hook
    self.increment_counter(
    ~~~~~~~~~~~~~~~~~~~~~~^
        counter=obj,
        ^^^^^^^^^^^^
    ...<3 lines>...
        amount=1,  # LOG ERROR COUNT TO PROMETHEUS
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/usr/local/lib/python3.13/site-packages/litellm/integrations/prometheus_services.py", line 131, in increment_counter
    counter.labels(labels, *additional_labels).inc(amount)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/prometheus_client/metrics.py", line 199, in labels
    raise ValueError('Incorrect label count')
ValueError: Incorrect label count

### Are you a ML Ops Team?

Yes

### What LiteLLM version are you on ?

v1.56.5

### Twitter / LinkedIn details

_No response_

[krrishdholakia]

able to repro