Update scala-library to 2.12.20

Author: scala-steward

build.sbt

@@ -14,7 +14,7 @@ organizationHomepage := Some(url("http://evolution.com"))
 
 scalaVersion := crossScalaVersions.value.head
 
-crossScalaVersions := Seq("2.13.11", "2.12.18", "3.3.0")
+crossScalaVersions := Seq("2.13.11", "2.12.20", "3.3.0")
 
 Compile / unmanagedSourceDirectories += {
   if (scalaVersion.value startsWith "2")