Hotfix to address the IOException in the SimpleDatabaseManager class, modified modifier and deleted useless test.

test/hhn/temp/project/DatabaseBadCasesTest.java

@@ -5,12 +5,8 @@ import hhn.temp.project.provider.SimpleDatabaseManager;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
-
-import java.io.IOException;
 import java.sql.SQLException;
 
-import static org.junit.jupiter.api.Assertions.*;
-
 public class DatabaseBadCasesTest {
 
   private DatabaseManager databaseManager;