[HACKERS] a typo in json.h

[Haifeng Liu]

Seems there is a trivial typo in json.h

diff --git a/src/include/utils/json.h b/src/include/utils/json.h
index 415787b..fa0d4fc 100644
--- a/src/include/utils/json.h
+++ b/src/include/utils/json.h
@@ -26,4 +26,4 @@ extern Datum row_to_json(PG_FUNCTION_ARGS);
 extern Datum row_to_json_pretty(PG_FUNCTION_ARGS);
 extern void  escape_json(StringInfo buf, const char *str);

-#endif   /* XML_H */
+#endif   /* JSON_H */