Update dependency org.apache.maven.plugins:maven-source-plugin to v2.4

Author: renovate[bot]

pom.xml

@@ -75,7 +75,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-source-plugin</artifactId>
-                <version>2.2.1</version>
+                <version>2.4</version>
                 <executions>
                     <execution>
                         <id>attach-sources</id>