Bump spark.version from 2.3.1 to 2.4.8

Bumps `spark.version` from 2.3.1 to 2.4.8.

Updates `org.apache.spark:spark-streaming_2.11` from 2.3.1 to 2.4.8

Updates `org.apache.spark:spark-core_2.11` from 2.3.1 to 2.4.8

---
updated-dependencies:
- dependency-name: org.apache.spark:spark-streaming_2.11
  dependency-version: 2.4.8
  dependency-type: direct:production
- dependency-name: org.apache.spark:spark-core_2.11
  dependency-version: 2.4.8
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pom.xml

@@ -76,7 +76,7 @@
     <jackson.core.version>2.8.11.1</jackson.core.version>
     <junit.version>4.12</junit.version>
     <slf4j.version>1.7.5</slf4j.version>
-    <spark.version>2.3.1</spark.version>
+    <spark.version>2.4.8</spark.version>
   </properties>
 
   <repositories>