Update scala-library, scala-reflect to 2.12.20 (apache#592)

Co-authored-by: scala-steward-asf[bot] <147768647+scala-steward-asf[bot]@users.noreply.github.com>

Author: scala-steward-asf[bot]

project/Dependencies.scala

@@ -33,7 +33,7 @@ object Dependencies {
 
   val scalafixVersion = _root_.scalafix.sbt.BuildInfo.scalafixVersion // grab from plugin
 
-  val scala212Version = "2.12.19"
+  val scala212Version = "2.12.20"
   val scala213Version = "2.13.14"
   val scala3Version = "3.3.3"
   val allScalaVersions = Seq(scala213Version, scala212Version, scala3Version)