### Body

Currently `start_date` is mandatory parameter.
For DAGs with `schedule=None` we can relax this requirement as no scheduling calculation needed so the `start_date` parameter isn't used.

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
tis: Sequence[TI]
            @classmethod
            def calculate(cls, unfinished_tis: Sequence[TI]) -> _UnfinishedStates:
                return cls(tis=unfinished_tis)
            @property
            def should_schedule(self) -> bool:
                return (
                    bool(self.tis)
                    and all(not t.task.depends_on_past for t in self.tis)
                    and all(t.task.max_active_tis_per_dag is None for t in self.tis)
                    and all(t.task.max_active_tis_per_dagrun is None for t in self.tis)
                    and all(t.state != TaskInstanceState.DEFERRED for t in self.tis)
                )
            def recalculate(self) -> _UnfinishedStates: