deps: update spark.version to v2.4.8 (#177)

Author: renovate-bot

pom.xml

@@ -19,7 +19,7 @@
     <encoding>UTF-8</encoding>
     <scala.version>2.11.12</scala.version>
     <scala.version.short>2.11</scala.version.short>
-    <spark.version>2.4.7</spark.version>
+    <spark.version>2.4.8</spark.version>
   </properties>
   <dependencies>
     <dependency>