Fixed XGBoost Example README (NVIDIA#2913)

* Changed split_mode to data_split_mode

* Fixed a merging error

examples/advanced/xgboost_secure/README.md

@@ -78,22 +78,22 @@ nvflare config -jt ../../../job_templates/
 
 # create horizontal job
 nvflare job create -force -w xgboost -j ./jobs/xgb_hori \
-    -f config_fed_server.conf secure_training=false split_mode=0 \
+    -f config_fed_server.conf secure_training=false data_split_mode=0 \
     -f config_fed_client.conf folder="/tmp/nvflare/xgb_dataset/horizontal_xgb_data"
 
 # create horizontal secure job
 nvflare job create -force -w xgboost -j ./jobs/xgb_hori_secure \
-    -f config_fed_server.conf secure_training=true split_mode=0 \
+    -f config_fed_server.conf secure_training=true data_split_mode=0 \
     -f config_fed_client.conf folder="/tmp/nvflare/xgb_dataset/horizontal_xgb_data"
 
 # create vertical job
 nvflare job create -force -w xgboost -j ./jobs/xgb_vert \
-    -f config_fed_server.conf secure_training=false split_mode=1 \
+    -f config_fed_server.conf secure_training=false data_split_mode=1 \
     -f config_fed_client.conf folder="/tmp/nvflare/xgb_dataset/vertical_xgb_data"
 
 # create vertical secure job
 nvflare job create -force -w xgboost -j ./jobs/xgb_vert_secure \
-    -f config_fed_server.conf secure_training=true split_mode=1 \
+    -f config_fed_server.conf secure_training=true data_split_mode=1 \
     -f config_fed_client.conf folder="/tmp/nvflare/xgb_dataset/vertical_xgb_data"
 
 ```