[Deepspeed] various fixes (#12058)

* replace deprecated config

* sub_group_size was too big

* complete deprecation removal

tests/deepspeed/ds_config_zero2.json

@@ -29,13 +29,16 @@
 
     "zero_optimization": {
         "stage": 2,
+        "offload_optimizer": {
+            "device": "cpu",
+            "pin_memory": true
+        },
         "allgather_partitions": true,
         "allgather_bucket_size": 2e8,
         "overlap_comm": true,
         "reduce_scatter": true,
         "reduce_bucket_size": 2e8,
-        "contiguous_gradients": true,
-        "cpu_offload": true
+        "contiguous_gradients": true
     },
 
     "gradient_accumulation_steps": "auto",