Lint: Tell users that backslashes are no longer necessary after => & |

[wxtim]

Edit: superseded by #6493

Closes #6456

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).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests are included (or explain why tests are not needed).
• Changelog entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• This is a feature, but a lint feature, so suitable to be added to a maintainance release.

[MetRonnie]

I think this should be part of S014

[wxtim]

I think that they should in time be, but at the moment they will not work if you are using compat mode Cylc 8 and Cylc 7 in Para||el, so I think that they should be an upgrade until Cylc 7 is more dead than it currently is.

[hjoliver]

"more dead" 😁

[hjoliver]

One typo detected and a couple of small tweaks suggested.

(It may be a bit picky, but I'd say "=>" etc., imply line continuation rather than being line continuation).

[MetRonnie]

This has added a new lint rule S014 on 8.3.x, however S014 is already a different rule on master (#6137), blocking sync PRs for the time being (#6489). I think this should be reverted and re-opened against master.