remove CYLC_WORKFLOW_NAME from many tests

[wxtim]

Another follow up to #4455 : Response to @oliver-sanders review.

Up against beta 3 because it probably doesn't make sense to have #4455 in but not this.

• 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).
• Applied any dependency changes to both setup.py and
  conda-environment.yml.
• Does not need tests (Changes to tests).
• No change log entry required (Covered by ~_W'FLOW_NAME ⇒ ~_W'FLOW_ID and ~_W'FLOW_NAME re-instated as Cylc7 consistent #4455 )
• No documentation update required.