Set reference version to 3.3.1-RC4

[Cherry-picked 2e35a7d]

Author: Kordyjan

project/Build.scala

@@ -81,7 +81,7 @@ object DottyJSPlugin extends AutoPlugin {
 object Build {
   import ScaladocConfigs._
 
-  val referenceVersion = "3.3.1-RC3"
+  val referenceVersion = "3.3.1-RC4"
 
   val baseVersion = "3.3.2-RC1"