Update to spark version

This article is refers to Spark version 2.4. Shouldnt it be 3.1 as its the latest supported version

Author: svchandramohan

articles/synapse-analytics/overview-what-is.md

@@ -30,7 +30,7 @@ ms.custom: ignite-fall-2021
 
 **Apache Spark for Azure Synapse** deeply and seamlessly integrates Apache Spark--the most popular open source big data engine used for data preparation, data engineering, ETL, and machine learning.
 
-* ML models with SparkML algorithms and AzureML integration for Apache Spark 2.4 with built-in support for Linux Foundation Delta Lake.
+* ML models with SparkML algorithms and AzureML integration for Apache Spark 3.1 with built-in support for Linux Foundation Delta Lake.
 * Simplified resource model that frees you from having to worry about managing clusters.
 * Fast Spark start-up and aggressive autoscaling.
 * Built-in support for .NET for Spark allowing you to reuse your C# expertise and existing .NET code within a Spark application.