Clarify warning for partition-driven DAGs in dags next-execution

[shleshaG]

What does this PR do?

Clarifies the warning message shown by airflow dags next-execution when no next
data interval can be determined, noting that this can also occur for
dataset- or partition-driven DAGs.

Why is this needed?

With AIP-76, partition-driven and dataset-driven DAGs may not have a
determinable next execution date. The previous message only mentioned
@once or None schedules, which could be misleading.

This change improves CLI clarity without altering behavior.

How was this tested?

• Manual verification of CLI output

Related issue

• Determine what next execution should do for partition-driven dags #61076

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[bugraoz93]

I didn't quite get the change here as explanation looks the same but I am expecting some kind of implementation for the issue. Maybe you can try to ask more questions there to understand exact change needs to be made

[potiuk]

Actualy - the right fix here will be to remove interval. In Airflow 3 we have schedule as the preferred way to specify schedule - other past ways are deprecated, so just removing interval will be enough - adding almost the same thing twice is quite confusing

[shleshaG]

@potiuk Thanks a lot for the clarification! That makes sense — I see now that updating the warning text alone is not sufficient.
Based on your guidance, I’ll update the implementation to remove usage of interval and rely solely on schedule, which aligns with the Airflow 3 scheduling model. I’ll push an updated commit shortly. Please let me know if there’s anything else I should watch out for.

[uranusjr]

There are actually more cases, once and none are simply the oldest ones (and probably the only ones when this message was first introduced).

Let’s change the entire message to something like This Dag may have a schedule that is not time-based, such as None or @once.