Fix/metric expire not working

[riptide-01]

Tests

func handlerHook(_ context.Context, input *pkg.HookInput) error {
	input.MetricsCollector.Set(metricName, 1, map[string]string{"test": "1"}, operation.WithGroup(metricGroup))
	input.MetricsCollector.Set(metricName2, 2, map[string]string{"test": "2"})
	input.MetricsCollector.Expire(metricGroup)
	return nil
}

Before:

After: