Small changes on "DAGs and Tasks documentation"

[JavierLopezT]

No description provided.

[JavierLopezT]

I have "broken" the tutorial dag file. It was made for being one actual dag split into different sections. However, I find it confusing because in each section there was just one part of the DAG, and in some cases, as the modified, I think it is useful to have the whole picture. So before fixing the static cheks, I would like some feedback on this, just in case I have to make other changes.

Also, I don't know if with the code the SEO can be improved, because if you search DAG documentation or similar in Google it doesn't appear. It doesn't even appear in the search of Airflow docs.

[github-actions]

The Workflow run is cancelling this PR. It has some failed jobs matching ^Pylint$,^Static checks,^Build docs$,^Spell check docs$,^Provider packages,^Checks: Helm tests$,^Test OpenAPI*.

[github-actions]

The Workflow run is cancelling this PR. It has some failed jobs matching ^Pylint$,^Static checks,^Build docs$,^Spell check docs$,^Provider packages,^Checks: Helm tests$,^Test OpenAPI*.

[KulykDmytro]

task.doc_md not rendering when

AIRFLOW__CORE__STORE_SERIALIZED_DAGS=True

at least on 1.10.15