Remove vestiges of authorisation layer removed in #3845

[MetRonnie]

Follow-up to #3845

This user field was being added here:

cylc-flow/cylc/flow/network/__init__.py

Lines 105 to 111 in d8c355a

	def deserialize(message: str) -> 'ResponseDict':
	"""Convert a JSON message string to dict with an added 'user' field."""
	# Abstract out the transport format in order to allow it to be changed
	# in future.
	msg = json.loads(message)
	msg['user'] = getpass.getuser() # assume this is the user
	return msg

and then dropped here:

cylc-flow/cylc/flow/network/authorisation.py

Lines 38 to 41 in 695445d

	def _call(self, *args, user='?', meta=None, **kwargs):
	if not meta:
	meta = {}
	return fcn(self, *args, meta=meta, **kwargs)

without actually doing anything

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
• Changelog entry not needed as invisible to users
• No docs needed
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[hjoliver]

LGTM