chore: drop Scala collection compat (#3434)

Author: ennru

project/Dependencies.scala

@@ -61,7 +61,6 @@ object Dependencies {
 
   val testkit = Seq(
     libraryDependencies := Seq(
-        "org.scala-lang.modules" %% "scala-collection-compat" % "2.7.0",
         "com.typesafe.akka" %% "akka-stream" % AkkaVersion,
         "com.typesafe.akka" %% "akka-stream-testkit" % AkkaVersion,
         "com.typesafe.akka" %% "akka-slf4j" % AkkaVersion,