Improve `record_lost_event` parameter documentation

[szokeasaurusrex]

data_category and item are mutually exclusive; only one should be provided at a time.

sentry-python/sentry_sdk/transport.py

Lines 133 to 142 in 31efa62

	def record_lost_event(
	self,
	reason, # type: str
	data_category=None, # type: Optional[str]
	item=None, # type: Optional[Item]
	):
	# type: (...) -> None
	"""This increments a counter for event loss by reason and
	data category.
	"""