Fix test/utils.py Twisted log formatting hack

[ShadowJonathan]

Apply the same fix from matrix-org/synapse#8335 onto the following lines:

sydent/tests/utils.py

Lines 234 to 245 in 66abd5b

	class ToTwistedHandler(logging.Handler):
	"""logging handler which sends the logs to the twisted log"""
	tx_log = twisted.logger.Logger()
	def emit(self, record):
	log_entry = self.format(record)
	log_level = record.levelname.lower().replace("warning", "warn")
	self.tx_log.emit(
	twisted.logger.LogLevel.levelWithName(log_level),
	log_entry.replace("{", r"(").replace("}", r")"),
	)

[anoadragon453]

@ShadowJonathan would you mind creating a similar PR for this as the one you did for Synapse?