Update scala-library, scala-reflect to 2.12.20 (#538)

Author: scala-steward

build.sbt

@@ -26,7 +26,7 @@ lazy val commonSettings =
   Seq(
     organization := "org.mockito",
     // Load version from the file so that Gradle/Shipkit and SBT use the same version
-    crossScalaVersions := Seq(currentScalaVersion, "2.12.19", "2.11.12"),
+    crossScalaVersions := Seq(currentScalaVersion, "2.12.20", "2.11.12"),
     scalafmtOnCompile  := true,
     scalacOptions ++= Seq(
       "-unchecked",