switch test to default sycl device

Author: Dmitry Razdoburdin

tests/python-sycl/test_sycl_training_continuation.py

@@ -13,7 +13,7 @@ def run_training_continuation(self, use_json):
         y = rng.randn(kRows)
         dtrain = xgb.DMatrix(X, y)
         params = {
-            "device": "sycl:cpu",
+            "device": "sycl",
             "max_depth": "2",
             "gamma": "0.1",
             "alpha": "0.01",