Remove support for =< Airflow 2.3.4 for new versions of DAG Factory

[cmarteepants]

This is prompted due to an issue with default_args not being mapped to Tasks in Task Groups (similar to #astronomer/astronomer-cosmos#1382). While this will be fixed in Airflow for 2.10/2.11, to have proper behaviour for earlier versions, we will need to hack around the limitation.

Which brings up a valid questions: At what point can we stop supporting older Airflow versions?

• We released 2.4 Sept 2022: As a quick action item, we should remove support for <2.3.4 as part of the next release.
• In addition, we should start thinking about formalizing compatibility ranges. In OSS Airflow, the expectation is for providers to only support Airflow versions that were released within the last 12 months. That may be too aggressive, but I'd like to come up with a good middle ground.

[cmarteepants]

@jroach-astronomer issue which prompted the question: #253