Update specs2-core to 4.21.0

Author: scala-steward

build.sbt

@@ -13,7 +13,7 @@ val jakartaVersion               = "3.1.0"
 val elVersion                    = "5.0.0"
 val jodaConvertVersion           = "2.2.4"
 val jodaTimeVersion              = "2.13.0"
-val specs2Version                = "4.20.9"
+val specs2Version                = "4.21.0"
 val zioVersion                   = "2.1.14"
 val `example-dependency-version` = "1.0.0-RC1"
 val supportCrossVersionList      = Seq(scala3_Version, scala2_13Version)