[coq] [travis] Re-enable Coq's test in CI
[coq] [travis] Re-enable Coq's test in CI

Closes #3207

Signed-off-by: Emilio Jesus Gallego Arias <a1debd7f3d9036292773dd21463eb601946b38d8@x80.org>

dra27/jbuilder,dra27/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder