Update cats-core, cats-kernel-laws, ... to 1.6.0
Update cats-core, cats-kernel-laws, ... to 1.6.0

ChristopherDavenport/http4s,aeons/http4s,ChristopherDavenport/http4s,rossabaker/http4s,http4s/http4s,aeons/http4s,rossabaker/http4s,aeons/http4s,ChristopherDavenport/http4s