Change output in weekly workflow from `wf` to `workflow`

[zkamvar]

I know wf is the name you use in the action, so changing it is a bit involved but ultimately, I think it would be best to rename it to something more descriptive, e.g. workflow.

Originally posted by @maxim-belkin in https://github.com/carpentries/lesson-example/pull/358#discussion_r710165077