How to remove a existing mapping in Spring Boot MVC?

Question

in an included library unfortunately the following is done:

@Bean
public WebMvcConfigurer webMvcConfigurerAdapter() {
   return new WebMvcConfigurer() {
      public void addViewControllers(ViewControllerRegistry registry) {
          registry.addViewController("/notFound").setViewName("forward:/index.html");
          ...
      }
   }
}

How and where can I remove this in my application afterwards? I would like to create a separate error page for it. For other errors except 404 the error page works.

Many greetings

Edit:

@Configuration
@Primary
public class SpringMvcConfiguration {

    @Bean
    @Primary
    public WebMvcConfigurer mywebMvcConfigurerAdapter() {
        return new WebMvcConfigurer() {
            public void addViewControllers(ViewControllerRegistry registry) {
                registry.addViewController("/login").setViewName("login");
                registry.addViewController("/error").setViewName("error");
                registry.addViewController("/notFound").setViewName("notFound");
                registry.addViewController("/").setViewName("forward:/index.html");
            }
        };
    }
}

That not work, it fowarded always to index.html