revert to jackson 2.18.4 (#124)

Author: pjfanning

build.sbt

@@ -284,7 +284,7 @@ lazy val library =
       val argonaut      = "6.3.11"
       val avro4s        = "4.1.2"
       val circe         = "0.14.13"
-      val jackson2      = "2.19.0"
+      val jackson2      = "2.18.4"
       val jackson3      = "3.0.0-rc4"
       val json4s        = "4.0.7"
       val jsoniterScala = "2.35.3"