Add whitespace after copyright header

Add an additional lines after the copyright header and before the
`package` declaration. This aligns with the style used by Spring
Framework.

Issue gh-8945

samples/javaconfig/preauth/src/main/java/org/springframework/security/samples/config/MessageSecurityWebApplicationInitializer.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.security.samples.config;
 
 import org.springframework.security.web.context.AbstractSecurityWebApplicationInitializer;

samples/javaconfig/preauth/src/main/java/org/springframework/security/samples/config/SecurityConfig.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.security.samples.config;
 
 import org.springframework.security.config.annotation.web.builders.HttpSecurity;

samples/javaconfig/preauth/src/test/java/org/springframework/security/samples/config/SecurityConfigTests.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.security.samples.config;
 
 import org.junit.Test;