Polish "Replace redundant call to class isInstance() with instanceof"

Closes gh-15554

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/server/OnManagementPortCondition.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/hateoas/HypermediaAutoConfigurationTests.java

@@ -70,7 +70,7 @@ public class HypermediaAutoConfigurationTests {
 		LinkDiscoverers discoverers = this.context.getBean(LinkDiscoverers.class);
 		assertThat(discoverers).isNotNull();
 		LinkDiscoverer discoverer = discoverers.getLinkDiscovererFor(MediaTypes.HAL_JSON);
-		assertThat(discoverer instanceof HalLinkDiscoverer).isTrue();
+		assertThat(discoverer).isInstanceOf(HalLinkDiscoverer.class);
 	}
 
 	@Test