Correct Mono import in LegacyHealthEndpointCompatibilityConfiguration

See gh-18571

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/health/LegacyHealthEndpointCompatibilityConfiguration.java

@@ -16,7 +16,7 @@
 
 package org.springframework.boot.actuate.autoconfigure.health;
 
-import io.micrometer.shaded.reactor.core.publisher.Mono;
+import reactor.core.publisher.Mono;
 
 import org.springframework.boot.actuate.health.HealthAggregator;
 import org.springframework.boot.actuate.health.HealthContributorRegistry;

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/health/HealthEndpointAutoConfigurationTests.java

@@ -47,6 +47,7 @@ import org.springframework.boot.actuate.health.ReactiveHealthIndicator;
 import org.springframework.boot.actuate.health.Status;
 import org.springframework.boot.actuate.health.StatusAggregator;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.runner.ReactiveWebApplicationContextRunner;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.context.annotation.Bean;
@@ -293,6 +294,12 @@ class HealthEndpointAutoConfigurationTests {
 		});
 	}
 
+	@Test // gh-18570
+	void runDoesNotFailWithoutReactorOnClasspath() {
+		this.contextRunner.withClassLoader(new FilteredClassLoader(Mono.class.getPackage().getName()))
+				.run((context) -> assertThat(context).hasNotFailed());
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class HealthIndicatorsConfiguration {