SpigotMC#3865: Bump Netty to 4.2.3-Final

Author: Janmm14

pom.xml

@@ -86,7 +86,7 @@
             <dependency>
                 <groupId>io.netty</groupId>
                 <artifactId>netty-bom</artifactId>
-                <version>4.2.1.Final</version>
+                <version>4.2.3.Final</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>