Simplify code

Author: liufengyun

compiler/src/dotty/tools/dotc/CompilationUnit.scala

@@ -95,11 +95,7 @@ class CompilationUnit protected (val source: SourceFile) {
    *  Depending on how fast the futures are run, sometimes it may
    *  observe the mutations in the later phase.
    */
-  def forcePickling()(using Context): Unit =
-    pickled = pickled.map { (sym, fn) =>
-      val bytes = fn()
-      (sym, () => bytes)
-    }
+  def forcePickling()(using Context): Unit = pickled.foreach(_._2())
 }
 
 object CompilationUnit {