Clarify what to place in tutorial `page-footer`fields

[MalikaIhle]

manual/authoring_tutorials/tutorial_template_repo.qmd

Line 217 in feb7152

* `page-footer` please update the year in the copyright if needed

[NeuroShepherd]

We'll probably still want to have some sort of content/info in the footer, but I believe it's correct that we won't include a copyright notice. I think it'll just be a link to the About page.