Use standard bean validation annotations that are new in 2.0

See gh-9969

spring-boot-samples/spring-boot-sample-actuator/src/main/java/sample/actuator/SampleController.java

@@ -21,7 +21,7 @@ import java.util.Date;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
-import org.hibernate.validator.constraints.NotBlank;
+import javax.validation.constraints.NotBlank;
 
 import org.springframework.context.annotation.Description;
 import org.springframework.http.MediaType;

spring-boot-samples/spring-boot-sample-web-groovy-templates/src/main/java/sample/groovytemplates/Message.java

@@ -18,7 +18,7 @@ package sample.groovytemplates;
 
 import java.util.Date;
 
-import org.hibernate.validator.constraints.NotEmpty;
+import javax.validation.constraints.NotEmpty;
 
 public class Message {
 
@@ -63,4 +63,5 @@ public class Message {
 	public void setSummary(String summary) {
 		this.summary = summary;
 	}
+
 }

spring-boot-samples/spring-boot-sample-web-ui/src/main/java/sample/web/ui/Message.java

@@ -18,7 +18,7 @@ package sample.web.ui;
 
 import java.util.Calendar;
 
-import org.hibernate.validator.constraints.NotEmpty;
+import javax.validation.constraints.NotEmpty;
 
 /**
  * @author Rob Winch
@@ -66,4 +66,5 @@ public class Message {
 	public void setSummary(String summary) {
 		this.summary = summary;
 	}
+
 }