Update Javadoc link to Netty 4.2

Author: acogoluegnes

pom.xml

@@ -457,7 +457,7 @@
           <source>8</source>
           <additionalOptions>-Xdoclint:none</additionalOptions>
           <links>
-            <link>https://netty.io/4.1/api/</link>
+            <link>https://netty.io/4.2/api/</link>
 <!--            <link>https://www.javadoc.io/doc/io.dropwizard.metrics/metrics-core/${metrics.version}/</link>-->
 <!--            <link>https://javadoc.io/doc/io.micrometer/micrometer-core/${micrometer.version}/</link>-->
           </links>