CI run against latest deps is failing

[github-actions]

See https://github.com/matrix-org/synapse/actions/runs/2991362357

[DMRobertson]

Run poetry run mypy
synapse/api/filtering.py:142: error: Value of type variable "_F" of function cannot be "Callable[[str], RoomID]"  [type-var]
synapse/api/filtering.py:147: error: Value of type variable "_F" of function cannot be "Callable[[str], UserID]"  [type-var]

[DMRobertson]

Likely python/typeshed#8673

[DMRobertson]

I think the functions decorated by cls_checks

synapse/synapse/api/filtering.py

Lines 142 to 149 in c52abc1

	@FormatChecker.cls_checks("matrix_room_id")
	def matrix_room_id_validator(room_id_str: str) -> RoomID:
	return RoomID.from_string(room_id_str)
	@FormatChecker.cls_checks("matrix_user_id")
	def matrix_user_id_validator(user_id_str: str) -> UserID:
	return UserID.from_string(user_id_str)

are supposed to return a bool, judging by https://github.com/python/typeshed/pull/8673/files#diff-f5e2679481de689eab96a68a36277093752a2cfa26602b4ca82e1178b01a726fL5-R6

It's not clear to me if we actually use the return value e.g. to parse as well as validate?

[DMRobertson]

See also python-jsonschema/jsonschema#958