use standard UnsupportedOperationException instead of NotImplementedException from internal packages

js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsProgram.java

@@ -8,7 +8,6 @@ import gnu.trove.TDoubleObjectHashMap;
 import gnu.trove.THashMap;
 import gnu.trove.TIntObjectHashMap;
 import org.jetbrains.annotations.NotNull;
-import sun.reflect.generics.reflectiveObjects.NotImplementedException;
 
 import java.util.Map;
 
@@ -144,6 +143,6 @@ public final class JsProgram extends SourceInfoAwareJsNode {
     @NotNull
     @Override
     public JsProgram deepCopy() {
-        throw new NotImplementedException();
+        throw new UnsupportedOperationException();
     }
 }

js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsProgramFragment.java

@@ -5,7 +5,6 @@
 package com.google.dart.compiler.backend.js.ast;
 
 import org.jetbrains.annotations.NotNull;
-import sun.reflect.generics.reflectiveObjects.NotImplementedException;
 
 /**
  * One independently loadable fragment of a {@link JsProgram}.
@@ -42,6 +41,6 @@ public class JsProgramFragment extends SourceInfoAwareJsNode {
     @NotNull
     @Override
     public JsProgramFragment deepCopy() {
-        throw new NotImplementedException();
+        throw new UnsupportedOperationException();
     }
 }