Polish access modifiers for test classes

See gh-27736

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/java/org/springframework/boot/maven/BuildInfoIntegrationTests.java

@@ -37,7 +37,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Andy Wilkinson
  */
 @ExtendWith(MavenBuildExtension.class)
-public class BuildInfoIntegrationTests {
+class BuildInfoIntegrationTests {
 
 	@TestTemplate
 	void buildInfoPropertiesAreGenerated(MavenBuild mavenBuild) {

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/java/org/springframework/boot/maven/EclipseM2eIntegrationTests.java

@@ -32,7 +32,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Phillip Webb
  */
-public class EclipseM2eIntegrationTests {
+class EclipseM2eIntegrationTests {
 
 	@Test // gh-21992
 	void pluginPomIncludesOptionalShadeDependency() throws Exception {

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/java/org/springframework/boot/maven/CustomLayersProviderTests.java

@@ -40,7 +40,7 @@ import static org.mockito.Mockito.mock;
  * @author Madhura Bhave
  * @author Scott Frederick
  */
-public class CustomLayersProviderTests {
+class CustomLayersProviderTests {
 
 	private CustomLayersProvider customLayersProvider;
 

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/java/org/springframework/boot/maven/DockerTests.java

@@ -31,7 +31,7 @@ import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException
  * @author Wei Jiang
  * @author Scott Frederick
  */
-public class DockerTests {
+class DockerTests {
 
 	@Test
 	void asDockerConfigurationWithDefaults() {