allow notification screen text to be translated (#10576)

The `noNotifications` string was not being used so changing it for
this purpose makes sense. Non-English users will see meaningful
text even before the new text is translated.

website/client/components/header/notificationsDropdown.vue

@@ -27,8 +27,8 @@ menu-dropdown.item-notifications(:right="true", @toggled="handleOpenStatusChange
       v-if="notificationsCount === 0"
     )
       .svg-icon(v-html="icons.success")
-      h2 You're all caught up!
-      p The notification fairies give you a raucous round of applause! Well done!
+      h2 {{ $t('noNotifications') }}
+      p {{ $t('noNotificationsText') }}
 </template>
 
 <style lang='scss' scoped>