remove test for KT-2257: cannot access private namespace var in multi-file namespace

compiler/testData/codegen/boxMultiFile/kt2257/1.kt

@@ -1,3 +0,0 @@
-fun box() = o + k
-
-private val o = "O"

compiler/testData/codegen/boxMultiFile/kt2257/2.kt

@@ -1,3 +0,0 @@
-private val k = "K"
-
-fun ignore() = o

compiler/tests/org/jetbrains/kotlin/codegen/generated/BlackBoxMultiFileCodegenTestGenerated.java

@@ -89,12 +89,6 @@ public class BlackBoxMultiFileCodegenTestGenerated extends AbstractBlackBoxCodeg
         doTestMultiFile(fileName);
     }
 
-    @TestMetadata("kt2257")
-    public void testKt2257() throws Exception {
-        String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxMultiFile/kt2257/");
-        doTestMultiFile(fileName);
-    }
-
     @TestMetadata("multifileClassPartsInitialization")
     public void testMultifileClassPartsInitialization() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxMultiFile/multifileClassPartsInitialization/");