Update references to loop-invariant-global-usage

[pR0Ps]

Looks like these were missed as part of #27

Was seeing the following error while re-testing #26 at 4bf47e0

$ perflint repro.py
Exception on node <Name.x l.5 at 0x10efcae90> in file '/tmp/repro.py'
Traceback (most recent call last):
  File "/tmp/venv-710/lib/python3.10/site-packages/pylint/utils/ast_walker.py", line 73, in walk
    callback(astroid)
  File "/tmp/venv-710/lib/python3.10/site-packages/perflint/for_loop_checker.py", line 324, in visit_name
    self.add_message("loop-invariant-global-usage", node=node)
  File "/tmp/venv-710/lib/python3.10/site-packages/pylint/checkers/base_checker.py", line 112, in add_message
    self.linter.add_message(
  File "/tmp/venv-710/lib/python3.10/site-packages/pylint/lint/pylinter.py", line 1629, in add_message
    message_definitions = self.msgs_store.get_message_definitions(msgid)
  File "/tmp/venv-710/lib/python3.10/site-packages/pylint/message/message_definition_store.py", line 65, in get_message_definitions
    for m in self.message_id_store.get_active_msgids(msgid_or_symbol)
  File "/tmp/venv-710/lib/python3.10/site-packages/pylint/message/message_id_store.py", line 130, in get_active_msgids
    raise UnknownMessageError(error_msg)
pylint.exceptions.UnknownMessageError: No such message id or symbol 'loop-invariant-global-usage'.

[tonybaloney]

Ouch. Nice spot. thanks