Make example consistent with paper.

1 job for master in 12 minutes and 3 seconds (queued for 8 minutes and 16 seconds)
Status Job ID Name Coverage
failed #48124


Name Stage Failure
failed Build
| - remove coq-stdpp           dev
| - remove num 1.2

The former state can be restored with:
opam switch import "/builds/iris/actris/opamroot/ocaml-base-compiler.4.07.1/.opam-switch/backup/state-20191121023941.export"
Or you can retry to install your package selection with:
opam install --restore
ERROR: Job failed: exit code 1