Fix potential type error & a few small mistakes

[MetRonnie]

Small change with no associated issue

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• No dependency changes
• tests are not needed
• No changelog entry as not known bug
• No docs needed
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[MetRonnie]

Another similar mistake spotted for the TaskPool.spawn_task() method (not to be confused with TaskEventsManager.spawn_func() mentioned before):

cylc-flow/cylc/flow/task_pool.py

Lines 1657 to 1664 in f30f0c2

	def spawn_task(
	self,
	name: str,
	point: 'PointBase',
	flow_nums: Set[int],
	force: bool = False,
	flow_wait: bool = False,
	) -> Optional[TaskProxy]:

flow_wait is incorrectly passed to the force argument in 2 places:

cylc-flow/cylc/flow/task_pool.py

Lines 744 to 745 in f30f0c2

	# ntask does not exist: spawn it in the flow.
	ntask = self.spawn_task(tdef.name, point, flow_nums, flow_wait)

cylc-flow/cylc/flow/task_pool.py

Lines 2015 to 2020 in f30f0c2

	def _set_prereqs_tdef(
	self, point, taskdef, prereqs, flow_nums, flow_wait
	):
	"""Spawn a future task and set prerequisites on it."""
	itask = self.spawn_task(taskdef.name, point, flow_nums, flow_wait)

[hjoliver]

(Ah, yeah I found that in my group-trigger branch, which I haven't exposed to you all yet)

[hjoliver]

LGTM, just one question.