Add a pass that removes `stablehlo.custom_call @Sharding`.
Add a pass that removes `stablehlo.custom_call @Sharding`.

These are the ops that originate from `tf.XlaSharding` ops, legalized by TF->StableHLO legalization passes.
These custom calls are not compatible with TFLite, so it needs to be removed before exporting to the TFLite flatbuffer.
