Update scala-library to 2.12.20

Author: scala-steward

build.sbt

@@ -2,7 +2,7 @@ import sbtcrossproject.CrossPlugin.autoImport.crossProject
 import _root_.org.typelevel.sbt.tpolecat.TpolecatPlugin.autoImport._
 import _root_.org.typelevel.scalacoptions.ScalacOptions
 
-lazy val scalaVersion212 = "2.12.19"
+lazy val scalaVersion212 = "2.12.20"
 lazy val scalaVersion213 = "2.13.13"
 lazy val scalaVersion3   = "3.3.3"
 lazy val scalaVersions   = List(scalaVersion212, scalaVersion213, scalaVersion3)