Metric dag.<dag_id>.<task_id>.duration is missing

### Apache Airflow version

Other Airflow 3 version (please specify below)

### If "Other Airflow 3 version" selected, which one?

3.0.6

### What happened?

Metric dag...duration is missing.

Found that the metric was removed in this particular commit - https://github.com/apache/airflow/pull/50141/files#diff-f660147b2482fe9eb7c256a6e9b5c0d8c0623fc31beaf5048e476e9bd1b7823b

Is this intended?

### What you think should happen instead?

Metric dag...duration should be available as per documentation.

### How to reproduce

Scrape airflow metrics and look for dag...duration metric.

### Operating System

Debian GNU/Linux 12 (bookworm)

### Versions of Apache Airflow Providers

apache-airflow-providers-celery==3.12.2
apache-airflow-providers-cncf-kubernetes==10.8.2
apache-airflow-providers-common-compat==1.7.3
apache-airflow-providers-common-io==1.6.2
apache-airflow-providers-common-sql==1.27.5
apache-airflow-providers-fab==2.4.1
apache-airflow-providers-ftp==3.13.2
apache-airflow-providers-http==5.3.3
apache-airflow-providers-imap==3.9.2
apache-airflow-providers-postgres==6.2.3
apache-airflow-providers-smtp==2.2.0
apache-airflow-providers-sqlite==4.1.2
apache-airflow-providers-standard==1.6.0

### Deployment

Other

### Deployment details

We use a slightly modified airflow helm chart

### 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)