Simplified contains BoundingBox code

The `if` didn't seem that useful anymore

src/engine/Collision/BoundingBox.ts

@@ -317,10 +317,7 @@ export class BoundingBox {
     if (val instanceof Vector) {
       return this.left <= val.x && this.top <= val.y && this.bottom >= val.y && this.right >= val.x;
     } else if (val instanceof BoundingBox) {
-      if (this.left <= val.left && this.top <= val.top && val.bottom <= this.bottom && val.right <= this.right) {
-        return true;
-      }
-      return false;
+      return this.left <= val.left && this.top <= val.top && val.bottom <= this.bottom && val.right <= this.right;
     }
     return false;
   }