Ok this is actually easy to solve and wont require you to redownload the whole game.

Step 1) go to the world of tanks website (download section) and check the version thats out right now. There will be a thing that says upgrade from #### to####. Remember only the "from" part

step 2) open your world of tanks folder in either games or program files

step 3) open the file "version".xml in notepad

step 4) change the version variable to the version before the update

step 5) launch wot

step 6) it will patch itself

step 7) enjoy