[LIVY-603][BUILD] Upgrade build spark version to 2.4.3

## What changes were proposed in this pull request?
Bump Spark 2.4 minor version to 2.4.3.

## How was this patch tested?
Existing test

Author: yihengwang <yihengwang@tencent.com>

Closes #179 from yiheng/bump_spark_2_4_3.

pom.xml

@@ -1050,15 +1050,15 @@
         </property>
       </activation>
       <properties>
-        <spark.scala-2.11.version>2.4.0</spark.scala-2.11.version>
+        <spark.scala-2.11.version>2.4.3</spark.scala-2.11.version>
         <spark.version>${spark.scala-2.11.version}</spark.version>
         <netty.spark-2.11.version>4.1.17.Final</netty.spark-2.11.version>
         <java.version>1.8</java.version>
         <py4j.version>0.10.7</py4j.version>
         <spark.bin.download.url>
-          https://archive.apache.org/dist/spark/spark-2.4.0/spark-2.4.0-bin-hadoop2.7.tgz
+          https://archive.apache.org/dist/spark/spark-2.4.3/spark-2.4.3-bin-hadoop2.7.tgz
         </spark.bin.download.url>
-        <spark.bin.name>spark-2.4.0-bin-hadoop2.7</spark.bin.name>
+        <spark.bin.name>spark-2.4.3-bin-hadoop2.7</spark.bin.name>
       </properties>
     </profile>