Update ipu_config.json

Lowering matmul_proportion and moving optimizer state offchip to avoid OOM on test 'groupbert_swag'

ipu_config.json

@@ -15,8 +15,8 @@
     4,
     4
   ],
-  "matmul_proportion": 0.22,
-  "optimizer_state_offchip": false,
+  "matmul_proportion": 0.1,
+  "optimizer_state_offchip": true,
   "optimum_version": "1.4.1",
   "output_mode": "final",
   "recompute_checkpoint_every_layer": true,