In order to preserve old behaviour, don't try to create RestClient-…

…based RegistrationClient, when `RestTemplateBuilder` bean is present.

spring-boot-admin-client/src/main/java/de/codecentric/boot/admin/client/config/SpringBootAdminClientAutoConfiguration.java

@@ -160,6 +160,7 @@ public RegistrationClient registrationClient(ClientProperties client) {
 
 	@Configuration(proxyBeanMethods = false)
 	@ConditionalOnBean(RestClient.Builder.class)
+	@ConditionalOnMissingBean(RestTemplateBuilder.class)
 	public static class RestClientRegistrationClientConfig {
 
 		@Bean