refactor(security): 移除 Customizer 的未使用导入

在 `PigxBootSecurityServerConfiguration.java` 中删除了未使用的 `Customizer` 导入，以保持代码整洁。

pigx-boot/src/main/java/com/pig4cloud/pigx/bootstrap/PigxBootSecurityServerConfiguration.java

@@ -36,7 +36,6 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.security.authentication.AuthenticationManager;
-import org.springframework.security.config.Customizer;
 import org.springframework.security.config.annotation.web.builders.HttpSecurity;
 import org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer;
 import org.springframework.security.config.annotation.web.configurers.HeadersConfigurer;