removed unused import

Author: wlanboy

src/main/java/com/wlanboy/javahttpclient/controller/DiagnosticController.java

@@ -13,7 +13,6 @@
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 
-import java.util.List;
 import java.util.Map;
 
 @RestController