Remove kafka_2.13 broker dependency from spring-kafka-test

  Removes the monolithic Scala-based Kafka broker dependency (kafka_2.13) in favor
  of the newer modular Java-based Kafka dependencies. The test module now relies
  exclusively on modular artifacts like kafka-server, kafka-metadata, and
  kafka-server-common, which provide the necessary test utilities without requiring
  the Scala runtime.

  - Remove scalaVersion variable from build configuration
  - Remove kafka_2.13 dependency and its test classifier variant
  - Rely on existing modular dependencies (kafka-server, kafka-metadata, kafka-server-common, etc.)

Signed-off-by: Soby Chacko <soby.chacko@broadcom.com>

Author: sobychacko

build.gradle

@@ -68,7 +68,6 @@ ext {
 	micrometerTracingVersion = '1.6.0-RC1'
 	mockitoVersion = '5.19.0'
 	reactorVersion = '2025.0.0-RC1'
-	scalaVersion = '2.13'
 	springBootVersion = '3.5.0' // docs module
 	springDataVersion = '2025.1.0-RC1'
 	springVersion = '7.0.0-RC1'
@@ -326,12 +325,6 @@ project ('spring-kafka-test') {
 		api "org.apache.kafka:kafka-server-common:$kafkaVersion"
 		api "org.apache.kafka:kafka-server-common:$kafkaVersion:test"
 		api "org.apache.kafka:kafka-streams-test-utils:$kafkaVersion"
-		api ("org.apache.kafka:kafka_$scalaVersion:$kafkaVersion") {
-			exclude group: 'commons-logging'
-		}
-		api ("org.apache.kafka:kafka_$scalaVersion:$kafkaVersion:test") {
-			exclude group: 'commons-logging'
-		}
 		api 'org.junit.jupiter:junit-jupiter-api'
 		api 'org.junit.platform:junit-platform-launcher'
 		optionalApi "org.hamcrest:hamcrest-core:$hamcrestVersion"