Make metrics endpoint back off without Actuator

Problem was introduced in "Create spring-boot-metrics module" which
is 1aea3c5 at the moment.

Author: wilkinsona

spring-boot-project/spring-boot-metrics/src/main/java/org/springframework/boot/metrics/autoconfigure/MetricsEndpointAutoConfiguration.java

@@ -35,7 +35,7 @@
  * @since 4.0.0
  */
 @AutoConfiguration(after = { MetricsAutoConfiguration.class, CompositeMeterRegistryAutoConfiguration.class })
-@ConditionalOnClass(Timed.class)
+@ConditionalOnClass({ ConditionalOnAvailableEndpoint.class, Timed.class })
 @ConditionalOnAvailableEndpoint(MetricsEndpoint.class)
 public class MetricsEndpointAutoConfiguration {