Update http4s-blaze-client, http4s-circe to 0.20.15
Update http4s-blaze-client, http4s-circe to 0.20.15

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