fix: stop double-counting unhandled_event in github webhook handler

it's handled here
https://github.com/codecov/codecov-api/blob/ca253c138ce000c16126f7b3693a7bbd90ce1086/webhook_handlers/views/github.py#L736

Author: matt-codecov

webhook_handlers/views/github.py

@@ -100,7 +100,6 @@ def validate_signature(self, request):
             raise PermissionDenied()
 
     def unhandled_webhook_event(self, request, *args, **kwargs):
-        self._inc_err("unhandled_event")
         return Response(data=WebhookHandlerErrorMessages.UNSUPPORTED_EVENT)
 
     def _get_repo(self, request):