Revert "Create MockStudentServiceImpl"

This reverts commit fd8e1dbc.

src/main/java/id/ac/ui/cs/advprog/tutorial0/service/MockStudentServiceImpl.java

-package id.ac.ui.cs.advprog.tutorial0.service;
-
-import id.ac.ui.cs.advprog.tutorial0.model.Student;
-import org.springframework.stereotype.Service;
-
-import java.util.List;
-
-@Service
-public class MockStudentServiceImpl implements StudentService{
-    @Override
-    public Student create(Student student) {
-        return null;
-    }
-
-    @Override
-    public List<Student> findAll() {
-        return null;
-    }
-}