[appindicator] Update manifest.ini

appindicator_integration/manifest.ini

 [info]
 name: Ayatana Appindicator integration
 short_name: appindicator_integration
-version: 1.1.20
+version: 1.1.21
 description: This plugin integrates Gajim with the Ayatana AppIndicator. You must have gir1.2-ayatanaappindicator3-0.1 installed to enable this plugin.
 homepage: https://dev.gajim.org/gajim/gajim-plugins/wikis/AppindicatorSupportPlugin
 authors: Denis Borenko <borenko@rambler.ru>