Update scala-library to 2.13.18 (#449)

Author: scala-steward

build.sbt

@@ -3,7 +3,7 @@ import com.typesafe.tools.mima.core._
 inThisBuild(
   List(
     scalaVersion := "2.12.20",
-    crossScalaVersions := Seq("2.12.20", "2.13.17", "3.3.7"),
+    crossScalaVersions := Seq("2.12.20", "2.13.18", "3.3.7"),
     scalacOptions ++= List("-release", "8"),
     javacOptions ++= List("-target", "8", "-source", "8"),
     organization := "com.thesamet.scalapb"