Fix sharding rule in jax test

`ValueError: Sharding rule has 1 operands, but the operation has 2 operands`

PiperOrigin-RevId: 762412744

Author: tomnatan30

tests/cache_key_test.py

@@ -181,7 +181,7 @@ def _cp_add(x, y):
     _cp_add.def_partition(
       infer_sharding_from_operands=_infer_sharding_from_operands,
       partition=_partition,
-      sharding_rule='i i -> i')
+      sharding_rule='..., ... -> ...')
 
     devices = np.asarray(jax.devices())
     with Mesh(devices, ('x',)) as m: