Update Netty to 4.1.59. (#837)

Author: michael-simons

pom.xml

@@ -64,7 +64,7 @@
       <dependency>
         <groupId>io.netty</groupId>
         <artifactId>netty-handler</artifactId>
-        <version>4.1.51.Final</version>
+        <version>4.1.59.Final</version>
       </dependency>
       <dependency>
         <groupId>io.projectreactor</groupId>