[Odometer] Remove Odometer expense splitting

[Julesssss]

Part of the Migrate Odometer project.

Odometer expenses should not be splittable. This was accidentally introduced here and we should remove it.

[melvin-bot]

Triggered auto assignment to @CortneyOfstad (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details. Please add this bug to a GH project, as outlined in the SO.

[Julesssss]

Internal PR nothing else needed here.