plugin: remove `.focus()`

src/plugins/Dashboard/index.js

@@ -109,7 +109,6 @@ module.exports = class DashboardUI extends Plugin {
       name: callerPluginName,
       icon: callerPluginIcon,
       type: callerPluginType,
-      focus: plugin.focus,
       render: plugin.render,
       isHidden: true
     }

src/plugins/Plugin.js

@@ -102,10 +102,6 @@ module.exports = class Plugin {
     }
   }
 
-  focus () {
-    return
-  }
-
   install () {
     return
   }