Fix coq-hott.8.6.dev package, which is the only hott package working with Coq 8.6.
Fix coq-hott.8.6.dev package, which is the only hott package working
with Coq 8.6.

coq/opam-coq-archive,ybertot/opam-coq-archive,mattam82/coq-opam-archive,gmalecha/opam-coq-archive,ybertot/opam-coq-archive,gmalecha/opam-coq-archive,ybertot/opam-coq-archive,gmalecha/opam-coq-archive,mattam82/coq-opam-archive,mattam82/coq-opam-archive