Backport "Set reference version to 3.3.1-RC3" to LTS (#19059)

Backports #18154 to the LTS branch.

PR submitted by the release tooling.
[skip ci]

Author: Kordyjan

project/Build.scala

@@ -81,7 +81,7 @@ object DottyJSPlugin extends AutoPlugin {
 object Build {
   import ScaladocConfigs._
 
-  val referenceVersion = "3.3.1-RC2"
+  val referenceVersion = "3.3.1-RC3"
 
   val baseVersion = "3.3.2-RC1"