Revert test change due to a GNUstep issue.
Revert test change due to a GNUstep issue.

The offset to this ivar is too big due to gnustep/libobjc2#10.

This reverts part of commit 08f7e831764aa60caa8d3c4184ac9b37a10fc906.

ngrewe/rust-objc,ngrewe/rust-objc,SSheldon/rust-objc,SSheldon/rust-objc