re-enable versionPolicy checking on Scala 3 (scala#497)

Author: SethTisue

build.sbt

@@ -4,12 +4,7 @@ ThisBuild / startYear := Some(2004)
 // I thought we could declare these in `ThisBuild` scope but no :-/
 val commonSettings = Seq(
   versionScheme := Some("early-semver"),
-  versionPolicyIntention := {
-    if (scalaVersion.value.startsWith("3"))
-      Compatibility.None
-    else
-      Compatibility.BinaryCompatible
-    }
+  versionPolicyIntention := Compatibility.BinaryCompatible,
 )
 
 lazy val root = project.in(file("."))