Replace log4j-slf4j-impl with slf4j-api in spring-kafka-test

Change spring-kafka-test to depend on slf4j-api instead of
log4j-slf4j-impl. This removes the forced Log4j binding from the
API surface, allowing consumers to choose their own SLF4J
implementation while still providing the compile-time dependency
required by Kafka's Utils class.

The slf4j-api dependency is needed because Kafka 4.x client libraries
use SLF4J for logging (e.g., Utils.closeQuietly() references
org.slf4j.Logger). Tests continue to use Log4j via the testRuntimeOnly
dependency configured globally.

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

Author: sobychacko

build.gradle

@@ -68,6 +68,7 @@ ext {
 	micrometerTracingVersion = '1.6.0-RC1'
 	mockitoVersion = '5.19.0'
 	reactorVersion = '2025.0.0-RC1'
+	slf4jVersion = '2.0.17'
 	springBootVersion = '3.5.0' // docs module
 	springDataVersion = '2025.1.0-RC1'
 	springVersion = '7.0.0-RC1'
@@ -314,7 +315,7 @@ project ('spring-kafka-test') {
 	description = 'Spring Kafka Test Support'
 
 	dependencies {
-		api "org.apache.logging.log4j:log4j-slf4j-impl:$log4jVersion"
+		api "org.slf4j:slf4j-api:$slf4jVersion"
 		api 'org.springframework:spring-context'
 		api 'org.springframework:spring-test'