Remove deprecated kwargs

ipu_config.json

@@ -1,13 +1,12 @@
 {
     "optimizer_state_offchip": false,
     "replicated_tensor_sharding": true,
-    "enable_half_first_order_momentum": true,
     "enable_half_partials": true,
     "recompute_checkpoint_every_layer": false,
     "device_iterations": 1,
     "inference_device_iterations": 4,
-    "replication_factor": {"pod4": 1, "pod8": 2, "pod16": 4, "pod32": 8, "pod64": 16, "default": 1},
-    "inference_replication_factor": {"pod4": 1, "pod8": 2, "pod16": 4, "pod32": 8, "pod64": 16, "default": 1},
+    "replication_factor": 1,
+    "inference_replication_factor": 1,
     "gradient_accumulation_steps": 32,
     "executable_cache_dir": "./exe_cache",
     "ipus_per_replica": 4,