Update copyright notices for setup (& other) files

[sadielbartholomew]

Whilst looking at the cylc-xtriggers repo I noticed the setup script had a copyright notice that did not include this year (cylc/cylc-xtriggers#5). Since the likelihood is that one template for these scripts was copied across repos & amended accordingly, I thought I would check that similar files in other repos were up-to-date.

In this case, it was not, & there were also three other instances remaining of outdated notices from a git grep "\-2018" (& the equivalent with a few other preceding years).

Trivial change, hence one reviewer sufficient.

This is a small change with no associated Issue.

Requirements 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).

• Does not need tests (reason: non-functional).

• No change log entry required (reason: invisible to users).

• No documentation update required.

[kinow]

Approved and will merge in a minute. First will just look at travis failures to see if we need to update the flaky tests list.

Thanks Sadie!

[kinow]

Tests that failed:

• ./tests/restart/23-hold-retry.t
• ./tests/hold-release/12-hold-then-retry.t

I was going to update #2894, but realized that #3286 includes changes for these two tests. So I am assuming it will be just fixed once that one is merged 🎉

Merging!