Update base version to 3.4.0 (scala#19768)

Part of scala#19679
Includes scala#18481

Author: Kordyjan

library/src/scala/runtime/ErasedFunction.scala

@@ -83,7 +83,7 @@ object DottyJSPlugin extends AutoPlugin {
 object Build {
   import ScaladocConfigs._
 
-  val referenceVersion = "3.3.1"
+  val referenceVersion = "3.4.0"
 
   val baseVersion = "3.4.2-RC1"
 
@@ -101,7 +101,7 @@ object Build {
    *  set to 3.1.3. If it is going to be 3.1.0, it must be set to the latest
    *  3.0.x release.
    */
-  val previousDottyVersion = "3.4.0-RC3"
+  val previousDottyVersion = "3.4.0"
 
   /** Version against which we check binary compatibility. */
   val ltsDottyVersion = "3.3.0"

project/Build.scala

@@ -86,7 +86,6 @@ val experimentalDefinitionInLibrary = Set(
 
   // New feature: functions with erased parameters.
   // Need erasedDefinitions enabled.
-  "scala.runtime.ErasedFunction", // will be removed (now using PolyFunction)
   "scala.quoted.Quotes.reflectModule.MethodTypeMethods.erasedParams",
   "scala.quoted.Quotes.reflectModule.MethodTypeMethods.hasErasedParams",
   "scala.quoted.Quotes.reflectModule.TermParamClauseMethods.erasedArgs",