Update dependency io.confluent:kafka-schema-registry-client to v8 (#3281)

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

Author: renovate[bot]

flink-formats/flink-avro-confluent-registry/pom.xml

@@ -33,7 +33,7 @@ under the License.
 
 	<properties>
 		<kafka.version>3.2.1</kafka.version>
-		<confluent.version>7.9.2</confluent.version>
+		<confluent.version>8.0.0</confluent.version>
 	</properties>
 
 	<repositories>