Update fs2-core to 3.9.4 (#637)

build.sbt

@@ -5,7 +5,7 @@ val scala_3   = "3.3.1"
 val V = new {
   val cats       = "2.10.0"
   val catsEffect = "3.5.3"
-  val fs2        = "3.9.3"
+  val fs2        = "3.9.4"
   val log4cats   = "2.6.0"
   val log4s      = "1.10.0"
   val scalaCheck = "1.17.0"