Bump log4j and slf4j versions

slf4j 1.7.25 -> 1.7.30
log4j 2.8.2 -> 2.13.3

Author: KarstenSchnitter

pom.xml

@@ -167,9 +167,9 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <jackson-jr.version>2.10.1</jackson-jr.version>
-        <slf4j.version>1.7.25</slf4j.version>
+        <slf4j.version>1.7.30</slf4j.version>
         <logback.version>1.2.3</logback.version>
-        <log4j2.version>2.8.2</log4j2.version>
+        <log4j2.version>2.13.3</log4j2.version>
         <buildnumber.plugin.version>1.4</buildnumber.plugin.version>
         <source.plugin.version>3.2.1</source.plugin.version>
         <jar.plugin.version>3.2.0</jar.plugin.version>