[doc] remove the doc about killing SparkContext [skip ci] (#7840)

doc/jvm/xgboost4j_spark_tutorial.rst

@@ -16,12 +16,6 @@ This tutorial is to cover the end-to-end process to build a machine learning pip
 * Building a Machine Learning Pipeline with XGBoost4J-Spark
 * Running XGBoost4J-Spark in Production
 
-.. note::
-
-  **SparkContext will be stopped by default when XGBoost training task fails**.
-
-  XGBoost4J-Spark 1.2.0+ exposes a parameter **kill_spark_context_on_worker_failure**. Set **kill_spark_context_on_worker_failure** to **false** so that the SparkContext will not be stopping on training failure. Instead of stopping the SparkContext, XGBoost4J-Spark will throw an exception instead. Users who want to re-use the SparkContext should wrap the training code in a try-catch block.
-
 .. contents::
   :backlinks: none
   :local: