Changelog: Do not line break in code in Markdown.

That confuses Gitlab's pretty-printer.
5 jobs for master in 9 minutes and 58 seconds (queued for 7 seconds)
Status Name Job ID Coverage
  Build
passed build-coq.8.6.1 #6656
fp-timing

00:02:59

passed build-coq.8.7.0 #6655
fp-timing

00:02:48

 
  Deploy
passed opam #6657

00:00:14

passed reverse-deps #6658

00:00:13

 
  Build More
passed build-coq.8.7.dev #6659
fp-timing

00:03:41