Migrate SpringJUnit4ClassRunner to SpringRunner

Replace all existing SpringJUnit4ClassRunner references with the new
SpringRunner alias.

Fixes gh-5292

spring-boot-samples/spring-boot-sample-tomcat/src/test/java/sample/tomcat/NonAutoConfigurationSampleTomcatApplicationTests.java

@@ -39,7 +39,7 @@ import org.springframework.context.annotation.Import;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.test.annotation.DirtiesContext;
-import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.junit4.SpringRunner;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -48,7 +48,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Dave Syer
  */
-@RunWith(SpringJUnit4ClassRunner.class)
+@RunWith(SpringRunner.class)
 @SpringApplicationConfiguration(NonAutoConfigurationSampleTomcatApplication.class)
 @WebIntegrationTest(randomPort = true)
 @DirtiesContext

spring-boot-samples/spring-boot-sample-tomcat/src/test/java/sample/tomcat/SampleTomcatApplicationTests.java

@@ -33,7 +33,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.test.annotation.DirtiesContext;
-import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.util.StreamUtils;
 import org.springframework.web.client.RestTemplate;
 
@@ -45,7 +45,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Dave Syer
  * @author Andy Wilkinson
  */
-@RunWith(SpringJUnit4ClassRunner.class)
+@RunWith(SpringRunner.class)
 @SpringApplicationConfiguration(SampleTomcatApplication.class)
 @WebIntegrationTest(randomPort = true)
 @DirtiesContext