J2K: no redundant type casts

#KT-6794 Fixed

j2k/testData/fileOrElement/codeSimplifications/RedundantTypeCast.java

@@ -0,0 +1,7 @@
+class C {
+    void foo(Object o) {
+        if (o instanceof String) {
+            int l = ((String) o).length();
+        }
+    }
+}

j2k/testData/fileOrElement/codeSimplifications/RedundantTypeCast.kt

@@ -0,0 +1,7 @@
+class C {
+    fun foo(o: Any) {
+        if (o is String) {
+            val l = o.length()
+        }
+    }
+}