Support only CrateDB versions >= 4.2.0

[chaudum]

Due to missing AL privileges in CrateDB < 4.2 there is a workaround to RESET allocations via the client

crate-operator/crate/operator/scale.py

Lines 416 to 426 in a19d944

	async def reset_allocation(namespace: str, pod_name: str, has_ssl: bool) -> None:
	"""
	Reset all temporary node deallocations to none.
	.. note::
	Ideally, we'd be using the system user to reset the allocation
	exclusions. However, `due to a bug
	<https://github.com/crate/crate/pull/10083>`_, this isn't possible in
	CrateDB <= 4.1.6. We therefore fall back to the "exce-in-container"
	approach that we also use during cluster bootstrapping.

In newer CrateDB versions, this workaround is obsolete and could be removed.