Update AdMob banner so they cover part of the game screen instead of reducing it (#6900)

* In most games, it's better to design the game with the size of the ad banner in mind - which will cover either part of the top or bottom of the screen. Previously, the game size was reduced which was making it difficult to properly design a game and would introduce bad looking black borders.

Extensions/AdMob/admobtools.ts

@@ -333,6 +333,7 @@ namespace gdjs {
         adUnitId,
         position: atTop ? 'top' : 'bottom',
         size: bannerRequestedAdSizeType,
+        offset: 0,
       });
 
       banner.on('load', () => {