Use log4j2 only for test

pom.xml

@@ -151,6 +151,7 @@
             <groupId>org.apache.logging.log4j</groupId>
             <artifactId>log4j-slf4j-impl</artifactId>
             <version>2.12.1</version>
+            <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>io.grpc</groupId>