Added missing change entry for the indexargs_form() fix.

Author: rouilj

CHANGES.txt

@@ -371,6 +371,10 @@ Fixed:
   (Ralf Schlatterbeck)
 - issue2550933 - Fix Traceback in cgi/templating.py when a string is
   passed to PasswordHTMLProperty::plain. (John Rouillard)
+- issue2550934 - templating.py-indexargs_form() returns id's as
+  space separated list not comma separated. This fixes the format of
+  the id url parameter when generated by indexargs_form. (John
+  Rouillard)
 
 2016-01-11: 1.5.1