[master] fix changelog entry

accidently had phrase repeated in
c077699ff43ddc2dff552b616044dab306f23666

ChangeLog

@@ -7,9 +7,8 @@
 
 614.	[func]		tmark
 	b10-d2: Initial DHCP-DDNS (a.k.a. D2) module implemented.
-	Currently it does nothing useful, except for does nothing useful,
-	except for providing the skeleton implementation to be expanded in
-	the future.
+	Currently it does nothing useful, except for providing the
+	skeleton implementation to be expanded in the future.
 	(Trac #2954, git 392c5ec5d15cd8c809bc9c6096b9f2bfe7b8c66a)
 
 613.	[func]		jinmei