Prevents BasicErrorControllerIntegrationTest to start another server

`BasicErrorControllerIntegrationTest` is handling the context in each test
and yet it starts a useless test via `@SpringBootTest`. This commit
removes the useless runner and associated annotations.

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/BasicErrorControllerIntegrationTests.java

 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -29,13 +29,10 @@ import javax.validation.constraints.NotNull;
 
 import org.junit.After;
 import org.junit.Test;
-import org.junit.runner.RunWith;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration;
 import org.springframework.boot.autoconfigure.web.BasicErrorControllerMockMvcTests.MinimalWebConfiguration;
-import org.springframework.boot.test.context.SpringBootTest;
-import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
 import org.springframework.boot.test.web.client.TestRestTemplate;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
@@ -45,8 +42,6 @@ import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.RequestEntity;
 import org.springframework.http.ResponseEntity;
-import org.springframework.test.annotation.DirtiesContext;
-import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.validation.BindException;
 import org.springframework.web.bind.MethodArgumentNotValidException;
 import org.springframework.web.bind.annotation.PostMapping;
@@ -66,9 +61,6 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Dave Syer
  * @author Stephane Nicoll
  */
-@RunWith(SpringRunner.class)
-@DirtiesContext
-@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
 public class BasicErrorControllerIntegrationTests {
 
 	private ConfigurableApplicationContext context;