emoji_picker: select recents tab by default

This saves a click to get at your most commonly used emoji.

src/components/emoji_picker/emoji_picker.js

@@ -31,7 +31,7 @@ const EmojiPicker = {
   data () {
     return {
       keyword: '',
-      activeGroup: 'standard',
+      activeGroup: 'recent',
       showingStickers: false,
       keepOpen: false
     }