Update to Netty 4.1.13.Final.

By: md_5 <git@md-5.net>

paper-server/pom.xml

@@ -61,7 +61,7 @@
         <dependency>
             <groupId>io.netty</groupId>
             <artifactId>netty-all</artifactId>
-            <version>4.1.12.Final</version>
+            <version>4.1.13.Final</version>
             <scope>compile</scope>
         </dependency>
         <!-- testing -->