Fix import ordering in SecurityNamespaceHandlerTests

Resolve Checkstyle SpringImportOrder violation by organizing imports
according to Spring's coding standards.

Signed-off-by: seongm1n <0411tjdals34@gmail.com>

Author: seongm1n

config/src/test/java/org/springframework/security/config/SecurityNamespaceHandlerTests.java

@@ -23,6 +23,7 @@
 import org.mockito.Mock;
 import org.mockito.MockedStatic;
 import org.mockito.junit.jupiter.MockitoExtension;
+
 import org.springframework.beans.factory.parsing.BeanDefinitionParsingException;
 import org.springframework.security.config.util.InMemoryXmlApplicationContext;
 import org.springframework.security.config.util.SpringSecurityVersions;