Fix of ConvertJavaInterfaceToClass test

Platform is trying to modify the class inheritance list during intension (see the test name above) action process but it cause a cross-language changes via PSI.
To make this possible LightClasses are supports this behaviour with a little support of it (inheritance list Add and inheritance list element Delete are supported).
It need's to be done for UL-classes in same way.

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixMultiFileTestGenerated.java

@@ -1395,7 +1395,6 @@ public class QuickFixMultiFileTestGenerated extends AbstractQuickFixMultiFileTes
         }
 
         @TestMetadata("kotlinInheritor.before.Main.java")
-        @Ignore("UltraLight classes does not support modification yet")
         public void testKotlinInheritor() throws Exception {
             runTest("idea/testData/quickfix/convertJavaInterfaceToClass/kotlinInheritor.before.Main.java");
         }