dag_processing.last_duration.<dag_file> metric missing

### Apache Airflow version Other Airflow 3 version (please specify below) ### If "Other Airflow 3 version" selected, which one? 3.0.6 ### What happened? Prior to version 3x, Airflow emitted the `dag_processing.last_duration.<dag_file>` metric. While working in MWAA with version 3.0.6, I noticed this metric is no longer available in CloudWatch. I verified MWAA is not excluding any metrics, so I expect the metric to be present. For a sanity check, I enabled StatsD in Breeze to see if the metric is emitted or not. I don't see the metric in Grafana. The other python file-level metric (dag_processing.last_run.seconds_ago.<dag_file>) is still emitted and visible in CloudWatch. The metric is still listed in the [Airflow metrics documentation](https://airflow.apache.org/docs/apache-airflow/3.0.6/administration-and-deployment/logging-monitoring/metrics.html#timers). ### What you think should happen instead? I expected the metric to be present. I find it useful when identifying python files that may need to be tuned for performance. ### How to reproduce For MWAA, create an MWAA environment with version 3.0.6 and upload a python file (with dag) to the Amazon S3 bucket. Once parsing takes place, attempt to find the metric in Amazon CloudWatch. ### Operating System AL2023 ### Versions of Apache Airflow Providers _No response_ ### Deployment Amazon (AWS) MWAA ### Deployment details This is a standard MWAA deployment. I did not add/modify any of the `[metrics]` config items. ### Anything else? _No response_ ### Are you willing to submit PR? - [ ] Yes I am willing to submit a PR! ### Code of Conduct - [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)