Update scalacheck to 1.18.0

Author: scala-steward

build.sbt

@@ -156,7 +156,7 @@ lazy val benchmarks = createModule("benchmarks")
 
 lazy val scalatest = "org.scalatest" %% "scalatest" % "3.2.18" % Test
 
-lazy val scalacheck = "org.scalacheck" %% "scalacheck" % "1.15.4" % Test
+lazy val scalacheck = "org.scalacheck" %% "scalacheck" % "1.18.0" % Test
 
 lazy val scalatestplus = "org.scalatestplus" %% "scalacheck-1-15" % "3.2.10.0" % Test