fix incorrect number of CHAOS RR class

RFC 2929

norefs

Change-Id: I4921ce688b04afb05e8179228c5a36379c745503

src/common/descriptor.h

@@ -35,7 +35,7 @@
  */
 enum knot_rr_class {
 	KNOT_CLASS_IN   =   1,
-	KNOT_CLASS_CH   =   2,
+	KNOT_CLASS_CH   =   3,
 	KNOT_CLASS_NONE = 254,
 	KNOT_CLASS_ANY  = 255
 };