Fix checkstyle errors

Author: ryanjbaxter

spring-cloud-kubernetes-discovery/src/test/java/org/springframework/cloud/kubernetes/discovery/HealthEventListenerConfiguration.java

@@ -38,7 +38,7 @@ HealthEventListener healthEventListener() {
 		return new HealthEventListener();
 	}
 
-	private static class HealthEventListener implements ApplicationListener<InstanceRegisteredEvent<?>> {
+	private static final class HealthEventListener implements ApplicationListener<InstanceRegisteredEvent<?>> {
 
 		@Override
 		public void onApplicationEvent(InstanceRegisteredEvent<?> event) {

spring-cloud-kubernetes-fabric8-config/src/test/java/org/springframework/cloud/kubernetes/fabric8/config/reload/ConfigReloadAutoConfigurationTest.java

@@ -439,7 +439,7 @@ void kubernetesReloadEnabledButSecretAndConfigDisabled() {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	private static class KubernetesClientTestConfiguration {
+	private static final class KubernetesClientTestConfiguration {
 
 		@ConditionalOnMissingBean(KubernetesClient.class)
 		@Bean

spring-cloud-kubernetes-fabric8-config/src/test/java/org/springframework/cloud/kubernetes/fabric8/config/reload/KubernetesConfigConfigurationTest.java

@@ -134,7 +134,7 @@ void kubernetesConfigWhenKubernetesEnabledAndKubernetesConfigDisabled() {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	private static class KubernetesClientTestConfiguration {
+	private static final class KubernetesClientTestConfiguration {
 
 		@ConditionalOnMissingBean(KubernetesClient.class)
 		@Bean

spring-cloud-kubernetes-fabric8-discovery/src/test/java/org/springframework/cloud/kubernetes/fabric8/discovery/Fabric8CatalogServicesWatchConfigurationTest.java

@@ -90,7 +90,7 @@ private void setup(String... env) {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	static class KubernetesClientTestConfiguration {
+	static final class KubernetesClientTestConfiguration {
 
 		@Bean
 		KubernetesClient kubernetesClient() {

spring-cloud-kubernetes-fabric8-discovery/src/test/java/org/springframework/cloud/kubernetes/fabric8/discovery/Fabric8DiscoveryClientAutoConfigurationPropertiesTests.java

@@ -90,7 +90,7 @@ private void setup(String... env) {
 	}
 
 	@Configuration(proxyBeanMethods = false)
-	static class KubernetesClientTestConfiguration {
+	static final class KubernetesClientTestConfiguration {
 
 		@Bean
 		KubernetesClient kubernetesClient() {