update a reference to long-gone double_neation module

2 jobs for master in 21 minutes and 29 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build-stdpp.dev-coq.8.11.1 #70451
fp

00:11:16

passed build-stdpp.dev-coq.dev #70452
fp

00:21:28