Auto merge of #2330 - RalfJung:notex, r=oli-obk

remove ancient tex files

These are the sources of `@solson's` original report, I think. They will remain available in the git history, but I don't think there is much point in still carrying them around on master. The readme links to their rendered PDFs:
- https://solson.me/miri-slides.pdf
- https://solson.me/miri-report.pdf

Author: bors