Update aflex-ayacc to the most up-to-date version
Pointing to the blog post because it explains how to use them together, but the repositories are here:
https://github.com/Ada-France/ayacc
https://github.com/Ada-France/aflex

Changes for makewithada.org and ada-europe.org about HTTP(S)
- Change www.makewithada.org to HTTP, since HTTPS raises error
- Change www.ada-europe.org to HTTPS, since it is working fine

Work around the last problems reported by the linter
This works around these problems:
README.md:191:3: https://matrix.to/#/#ada-lang_Lobby:gitter.im remark-lint:double-link
README.md:199:112: https://matrix.to/#/#ada-lang:matrix.org remark-lint:double-link
Which are due to an issue in the linter: https://github.com/Scrum/remark-lint-double-link/pull/10
Closes #107