Update links on training catalogue with new presentation

[Scottan]

Following #104

[andrewgait]

OK, so putting the slides into a documents directory does not appear to have worked - https://uomresearchit.github.io/Programming-With-Python/documents/programming_with_python_in_person_slides.pdf is giving me a 404. I'm not sure why it's treated differently to other directories in that location but perhaps data and fig are special (directory) names that the lesson builder looks for. So we need to fix this in some way so that users can download the slides in the same way they download the zip file from the data directory at the start - I suppose one quick fix is to just put the slides in the data directory? @Scottan any other ideas?

[Scottan]

This link at least takes you to the pdf:

https://github.com/UoMResearchIT/Programming-With-Python/blob/4578317607e7d32512e5d392f6bcddf367beb472/episodes/documents/programming_with_python_in_person_slides.pdf

The students can download them from there if they want, I think that's good enough. They don't really need the slides for the course, the main thing is the link to the notes which we'll share in a group chat or something.