Remove deprecated kwargs

ipu_config.json

@@ -3,13 +3,12 @@
   "recompute_checkpoint_every_layer": true,
   "optimizer_state_offchip": true,
   "replicated_tensor_sharding": true,
-  "enable_half_first_order_momentum": true,
   "enable_half_partials": true,
   "device_iterations": 1,
-  "replication_factor": {"pod4": 1, "pod8": 2, "pod16": 4, "pod32": 8, "pod64": 16, "default": 1},
+  "replication_factor": 1,
   "gradient_accumulation_steps": 16,
   "inference_device_iterations": 4,
-  "inference_replication_factor": {"pod4": 1, "pod8": 2, "pod16": 4, "pod32": 8, "pod64": 16, "default": 1},
+  "inference_replication_factor": 1,
   "executable_cache_dir": "./exe_cache",
   "ipus_per_replica": 4,
   "layers_per_ipu": [0, 4, 4, 4],