Update coq-hott.8.6.dev to track the new V8.6 tag
Update coq-hott.8.6.dev to track the new V8.6 tag

The master branch will soon be incompatible with v8.7
ybertot/opam-coq-archive,gmalecha/opam-coq-archive,ybertot/opam-coq-archive,ybertot/opam-coq-archive,mattam82/coq-opam-archive,mattam82/coq-opam-archive,gmalecha/opam-coq-archive,mattam82/coq-opam-archive,gmalecha/opam-coq-archive,coq/opam-coq-archive