Bump io.netty:netty-transport-native-kqueue (spiffe#379)

Bumps [io.netty:netty-transport-native-kqueue](https://github.com/netty/netty) from 4.2.7.Final to 4.2.8.Final.
- [Commits](netty/netty@netty-4.2.7.Final...netty-4.2.8.Final)

---
updated-dependencies:
- dependency-name: io.netty:netty-transport-native-kqueue
  dependency-version: 4.2.8.Final
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]

build.gradle

@@ -25,7 +25,7 @@ subprojects {
         shadowVersion = '8.1.1'
 
         //IMPORTANT: This must be in sync with the shaded netty version in gRPC
-        nettyVersion = '4.2.7.Final'
+        nettyVersion = '4.2.8.Final'
     }
 
     apply plugin: 'java-library'