Remove redundant execution_runtime_callbacks_executed_total metric

We have added few metrics for scheduled transactions implementation, including callbacksExecutedCount and callbacksExecutedTotal. The [callbacksExecutedTotal](https://github.com/onflow/flow-go/blob/78c4a1353a160abe2078b741af209ee38f03c3e9/module/metrics/execution.go#L102) metric duplicates sum portion of callbacksExecutedCount histogram metric and can be removed.