Update http4s-blaze-client, http4s-circe to 0.21.15

Author: 47erbot

build.sbt

@@ -15,7 +15,7 @@ lazy val V = new {
   val cats: String                = "2.3.1"
   val collectioncompat: String    = "2.3.2"
   val github4s: String            = "0.27.1"
-  val http4s: String              = "0.21.14"
+  val http4s: String              = "0.21.15"
   val runtime: String             = "0.6.4"
   val scala: String               = "2.13.3"
   val scala212: String            = "2.12.12"