MTb tutorials TODOs

@cstritt @pvanheus @hexylena: just creating an issue to track what final edits/polishing to do for these tutorials (after the course next week) Feel free to comment here with things you think of (or encounter during teaching).

Tutorials are currently in a draft "evolution" topic:
- https://training.galaxyproject.org/training-material/topics/evolution/tutorials/mtb_transmission/tutorial.html
- https://training.galaxyproject.org/training-material/topics/evolution/tutorials/mtb_phylogeny/tutorial.html

TODOs:
- [ ] Decide where to put these (rename metagenomics to "microbial analysis" and create an MTb subtopic?)
- [ ] Define prerequisites and follow-up tutorials in metadata (e.g. the videos)
- [ ] Remove mentions of the course
- [ ] Use citations properly, everywhere (mostly the variant-analysis tutorial)
- [ ] Add some topic/tutorial FAQs
- [ ] Remove numbering from question boxes
- [ ] consider merging question boxes