Remove duplicated lines in release notes.

Author: martignoni

CHANGELOG.md

@@ -13,11 +13,6 @@ This project adheres to [Semantic Versioning](http://semver.org/) and follow pri
 - Wi-Fi invalid SSIDs aren't allowed anymore (issue #30).
 - Prevent potential bugs due to not validated settings (issue #30).
 
-## Version 1.7, 2017-09-11
-### Added
-- Possibility to have an open (i.e. without password) Wi-Fi network (issue #22). Feature dedicated to @christian-westphal.
-- Wi-Fi channel selection depends on regulatory domain defined in `/etc/hostapd/hostapd` (issue #23)
-
 ## Version 1.7.1, 2017-09-13
 ### Fixed
 - Re-added removed strings to fix issue #25.