Remove .github/workflows/linkcheck.yml

[Araneidae]

In light of PR #64 I suggest we simply delete .github/workflows/linkcheck.yml.

I understand from Giles that our skeleton is now obsolete?

[AlexanderWells-diamond]

Agreed - we aren't using it and so may as well delete it.

As some point we should look at migrating to the Python Copier Template.