chore: update scala3Next to 3.9.0-RC1

Motivation:
Scala 3.9.0-RC1 is available and should be tested as the next Scala version.

Modification:
Update scala3Next version from 3.8.4 to 3.9.0-RC1.

Result:
Build will use Scala 3.9.0-RC1 as the next Scala version.

Tests:
Not run - version bump only

References:
None - version bump

Author: He-Pin

project/Dependencies.scala

@@ -44,7 +44,7 @@ object Dependencies {
 
   val scala213Version = "2.13.18"
   val scala3Version = "3.3.8"
-  val scala3NextVersion = "3.8.4"
+  val scala3NextVersion = "3.9.0-RC1"
   val publishedScalaVersions = Seq(scala213Version, scala3Version)
 
   val reactiveStreamsVersion = "1.0.4"