Improve Airflow core docs regarding Dag versioning (AIP-63)

### Apache Airflow version

3.1.6

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

_No response_

### What happened?

A task, when I need to clear a task in history, I find that there is no small square in this task, and the position of the small square is empty, so I can't jump to the task interface and can't clear it.

### What you think should happen instead?

For example, airflow2.x should be a white square under normal circumstances.

### How to reproduce

Modify the task logic of dag, for example: change a->b to a->b->c

### Operating System

Ubuntu 24.04 LTS

### Versions of Apache Airflow Providers

_No response_

### Deployment

Other

### Deployment details

_No response_

### 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)