Refine Kotlin serialization converters/codecs conditions

This commit is a follow-up of 34410 to refine the activation conditions
of Kotlin serialization converters/codecs.

Closes gh-34438

spring-web/src/test/java/org/springframework/web/client/RestTemplateTests.java

@@ -108,14 +108,16 @@ class RestTemplateTests {
 		template.setErrorHandler(errorHandler);
 	}
 
-	@Test // gh-29008
-	void defaultMessageConvertersWithKotlinSerialization() {
+	@Test
+	void defaultMessageConvertersWithoutKotlinSerialization() {
 		RestTemplate restTemplate = new RestTemplate();
 		List<HttpMessageConverter<?>> httpMessageConverters = restTemplate.getMessageConverters();
 		assertThat(httpMessageConverters).extracting("class").containsOnlyOnce(
-			KotlinSerializationJsonHttpMessageConverter.class,
 			MappingJackson2HttpMessageConverter.class
 		);
+		assertThat(httpMessageConverters).extracting("class").doesNotContain(
+				KotlinSerializationJsonHttpMessageConverter.class
+		);
 	}
 
 	@Test