Problem: recently gitlab changed the way URLs are formed, specifically:
1. There is `/-/` in many URLs such as
https://gitlab.com/morley-framework/morley/-/issues.
2. Because of that some relative links like `../blob/foo` are broken.
3. And of course many links are a bit obsolete because they get
redirected.

Solution:
1. Apparently now we can use saner links in MR templates, e. g.
just `README.md` instead of `../blob/master/README.md`. So we do it.
2. Obsolete links are updated to include this `/-` thing.