Go to your Device's settings, click "applications", then to the subtopic "Installed apps" , find the tanki app with its logo, click on the "storage" option and then finally click on the option "clear cache".
Example: -      

Yes I saw that too and went to check in the container section about any unknown update, but it was just a reminder of recent update of the weekly containers, that the new rewards are different from previous ones. Nothing new ^^