Converter tests:

Change test data files extension to "java"

j2k/tests/testData/ast/issues/kt-893.java

@@ -0,0 +1,10 @@
+//file
+package demo;
+
+class Test {
+  void test() {
+    for(int i = 0; i < 10; ++i) {
+      System.out.println(i)
+    }
+  }
+}