Bump netty.version from 4.2.4.Final to 4.2.6.Final (#2501)

Bumps `netty.version` from 4.2.4.Final to 4.2.6.Final.

Updates `io.netty:netty-codec-http` from 4.2.4.Final to 4.2.6.Final
- [Commits](https://github.com/netty/netty/compare/netty-4.2.4.Final...netty-4.2.6.Final)

Updates `io.netty:netty-handler` from 4.2.4.Final to 4.2.6.Final
- [Commits](https://github.com/netty/netty/compare/netty-4.2.4.Final...netty-4.2.6.Final)

Updates `io.netty:netty-handler-proxy` from 4.2.4.Final to 4.2.6.Final
- [Commits](https://github.com/netty/netty/compare/netty-4.2.4.Final...netty-4.2.6.Final)

Updates `io.netty:netty-transport-native-epoll` from 4.2.4.Final to 4.2.6.Final
- [Commits](https://github.com/netty/netty/compare/netty-4.2.4.Final...netty-4.2.6.Final)

Updates `io.netty:netty-transport-native-kqueue` from 4.2.4.Final to 4.2.6.Final
- [Commits](https://github.com/netty/netty/compare/netty-4.2.4.Final...netty-4.2.6.Final)

---
updated-dependencies:
- dependency-name: io.netty:netty-codec-http
  dependency-version: 4.2.6.Final
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: io.netty:netty-handler
  dependency-version: 4.2.6.Final
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: io.netty:netty-handler-proxy
  dependency-version: 4.2.6.Final
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: io.netty:netty-transport-native-epoll
  dependency-version: 4.2.6.Final
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: io.netty:netty-transport-native-kqueue
  dependency-version: 4.2.6.Final
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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