[xla:gpu] Remove `GatherSimplifier` and `ScatterSimplifier` from `runSPMDPasses`, to avoid breaking the parallel dimensions pattern for propagation and partitioning in GSPMD.
[xla:gpu] Remove `GatherSimplifier` and `ScatterSimplifier` from `runSPMDPasses`, to avoid breaking the parallel dimensions pattern for propagation and partitioning in GSPMD.

Those passes are applied in `RunOptimizationPasses` which is after partitioning.
