Update dependency io.netty:netty-bom to v4.2.1.Final (#1990)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

pom.xml

@@ -57,7 +57,7 @@
         <!-- upper bounds conflict -->
         <groupId>io.netty</groupId>
         <artifactId>netty-bom</artifactId>
-        <version>4.2.0.Final</version>
+        <version>4.2.1.Final</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>