Add a comment for TestJacksonFilter

Author: dmikurube

src/test/java/org/embulk/util/json/TestJacksonFilter.java

@@ -32,6 +32,7 @@
 public class TestJacksonFilter {
     @Test
     public void testFilterSequenceSkippingNonMatch() throws IOException {
+        // This |parser| returns only {"bar":"baz"} and {"bar":"qux"}, with just skipping {"xxx":{"yyy":"zzz"}}.
         final com.fasterxml.jackson.core.JsonParser parser = createFilteredParser(
                 "{\"foo\":{\"bar\":\"baz\"}}{\"xxx\":{\"yyy\":\"zzz\"}}{\"foo\":{\"bar\":\"quux\"}}",
                 JsonPointer.compile("/foo"));