Polish

As `validation-api` 2 is available by default, this commit adds the
integration test as a regular test case. The integration test is kept to
exercise what happens in a standard project.

See gh-11512

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/pom.xml

@@ -20,6 +20,11 @@
 			<artifactId>lombok</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>javax.validation</groupId>
+			<artifactId>validation-api</artifactId>
+			<scope>test</scope>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-test-support</artifactId>