Remove Kafka libraries for Scala 2.12 from dependency management

Kafka 4.0 dropped support for Scala 2.12, so the
`kafka-streams-scala_2.12` and `kafka_2.12` libraries should not be
dependency-managed along with the rest of the Kafka 4.1.0 libraries.

See gh-47991

Signed-off-by: Scott Frederick <scottyfred@gmail.com>

Author: scottfrederick

platform/spring-boot-dependencies/build.gradle

@@ -1189,14 +1189,9 @@ bom {
 				"kafka-storage",
 				"kafka-storage-api",
 				"kafka-streams",
-				"kafka-streams-scala_2.12",
 				"kafka-streams-scala_2.13",
 				"kafka-streams-test-utils",
 				"kafka-tools",
-				"kafka_2.12",
-				"kafka_2.12" {
-					classifier = "test"
-				},
 				"kafka_2.13",
 				"kafka_2.13" {
 					classifier = "test"