Update scalacheck to 1.15.0-RC1 (#124)

Author: scala-steward

build.sbt

@@ -46,7 +46,7 @@ lazy val junit = project.in(file("junit"))
 lazy val scalacheck = project.in(file("scalacheck"))
   .settings(commonSettings)
   .settings(
-    libraryDependencies += "org.scalacheck" %% "scalacheck" % "1.15.0-M1" withDottyCompat(scalaVersion.value),
+    libraryDependencies += "org.scalacheck" %% "scalacheck" % "1.15.0-RC1" withDottyCompat(scalaVersion.value),
     Test / fork := true,
     Test / testOptions += Tests.Argument(TestFrameworks.ScalaCheck, "-workers", "1", "-minSize", "0", "-maxSize", "4000", "-minSuccessfulTests", "5"),
     publish / skip := true