Fix filename on Changelog item

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/ChangeLog.d/rm-ticket-lifetime-option b/ChangeLog.d/rm-ticket-lifetime-option.txt
similarity index 100%
rename from ChangeLog.d/rm-ticket-lifetime-option
rename to ChangeLog.d/rm-ticket-lifetime-option.txt