upgrade netty to address CVE-2020-11612

The owasp checker is failing with the following. I looked and seems like a DOS attack vector "The ZlibDecoders in Netty 4.1.x before 4.1.46 allow for unbounded memory allocation while decoding a ZlibEncoded byte stream. An attacker could send a large ZlibEncoded byte stream to the Netty server, forcing the server to allocate all of its free memory to a single decoder."

[ERROR] Failed to execute goal org.owasp:dependency-check-maven:5.3.0:check (default-cli) on project zookeeper:
[ERROR]
[ERROR] One or more dependencies were identified with vulnerabilities that have a CVSS score greater than or equal to '0.0':
[ERROR]
[ERROR] netty-handler-4.1.45.Final.jar: CVE-2020-11612
[ERROR] netty-common-4.1.45.Final.jar: CVE-2020-11612
[ERROR] netty-buffer-4.1.45.Final.jar: CVE-2020-11612
[ERROR] netty-transport-4.1.45.Final.jar: CVE-2020-11612
[ERROR] netty-resolver-4.1.45.Final.jar: CVE-2020-11612
[ERROR] netty-codec-4.1.45.Final.jar: CVE-2020-11612
[ERROR] netty-transport-native-epoll-4.1.45.Final.jar: CVE-2020-11612
[ERROR] netty-transport-native-unix-common-4.1.45.Final.jar: CVE-2020-11612
[ERROR]