We keep link as code so that it's still visible, but not as a link so
it doesn't break link checkers.

We had 14, this should bring us below 10.

Closes: tpo/anti-censorship/team#4

See: tpo/anti-censorship/gettor-project/gettor#77

I feel the GitLab migration documentation belongs there, and could be
helpful to not pretend Trac never existed...

This reverts commit:

6a447183 remove link to dead trac page
1735010a remove trac documentation now that it is retired