PLT-3901 send different push message when only images attached (#6672)

i18n/en.json

@@ -1643,6 +1643,10 @@
     "id": "api.post.send_notifications_and_forget.push_non_mention",
     "translation": " posted in "
   },
+  {
+    "id": "api.post.send_notifications_and_forget.push_image_only",
+    "translation": " Uploaded one or more files "
+  },
   {
     "id": "api.post.send_notifications_and_forget.push_notification.error",
     "translation": "Failed to send push device_id={{.DeviceId}}, err={{.Error}}"