move val outside constructor

scala/scala3#8931

Author: martijnhoekstra

util-core/src/main/scala/com/twitter/util/Disposable.scala

@@ -94,9 +94,8 @@ trait Managed[+T] { selfT =>
    * Compose a new managed resource that depends on `this' managed resource.
    */
   def flatMap[U](f: T => Managed[U]): Managed[U] = new Managed[U] {
+    val t = selfT.make()
     def make() = new Disposable[U] {
-      val t = selfT.make()
-
       val u =
         try {
           f(t.get).make()