[birthday_reminder] Update manifest.ini

birthday_reminder/manifest.ini

 [info]
 name: Birthday reminder
 short_name: birthday_reminder
-version: 1.2.0
+version: 1.2.1
 description: Reminds you if a contact of yours has birthday
 authors: Evgeniy Popov <evgeniypopov@gmail.com>
+ Philipp Hörist <philipp@hoerist.com>
 homepage: https://dev.gajim.org/gajim/gajim-plugins/wikis/BirthdayReminderPlugin
 min_gajim_version: 1.1.91
 max_gajim_version: 1.2.90