Update dependency io.confluent:kafka-connect-avro-data to v8

Author: renovate[bot]

build.gradle.kts

@@ -25,7 +25,7 @@ repositories {
 
 dependencies {
     val kafkaVersion by extra("2.5.1")
-    val confluentVersion by extra("5.5.14")
+    val confluentVersion by extra("8.1.0")
     val kotestVersion by extra("4.2.5")
     val junitVersion by extra("5.7.0")
     implementation(kotlin("stdlib-jdk8"))