remove maven jarjar plugin (#773)

This is not bound to any executions so I don't think we're using it.

Author: elharo

pom.xml

@@ -281,11 +281,6 @@
           <artifactId>maven-deploy-plugin</artifactId>
           <version>2.8.2</version>
         </plugin>
-        <plugin>
-          <groupId>org.sonatype.plugins</groupId>
-          <artifactId>jarjar-maven-plugin</artifactId>
-          <version>1.9</version>
-        </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-source-plugin</artifactId>