github: fix yaml linter

[sxa]

Checklist

• commit message has one of the standard prefixes
• faq.md updated if appropriate
• other documentation is changed or added (if applicable)
• playbook changes run through VPC or QPC (if you have access)
• VPC/QPC not applicable for this PR
• for inventory.yml changes, bastillion/nagios/jenkins updated accordingly

Lots of fixes that are now being flagged in my one-line PR change to an unrelated file at #3398 (comment)

Noting that all these changes break the use of git blame or the equivalent in the UI so you will no longer be able to easily tell who made a change but c'est la vie ... Or as @karianna would say "That's why we can't have nice things" ;-)

[sxa]

Linter checks do not appear to be configured to run on changes to .github/workflow but are covering them, so I've added that into the checks too.

[sxa]

I'm going to cancel this on the basis that the checks that were failing in the other PR stopped failing when I re-ran it. Not clear why but I don't really want to spend any more time on this.