Revert "Remove invalid check for String-based FactoryBean.OBJECT_TYPE_ATTRIBUTE"

This reverts commit 279f8221a5.

See gh-36659

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/mock/mockito/MockitoPostProcessorTests.java

@@ -73,6 +73,18 @@ class MockitoPostProcessorTests {
 					+ " expected a single matching bean to replace but found [example1, example3]");
 	}
 
+	@Test
+	void canMockBeanProducedByFactoryBeanWithStringObjectTypeAttribute() {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		MockitoPostProcessor.register(context);
+		RootBeanDefinition factoryBeanDefinition = new RootBeanDefinition(TestFactoryBean.class);
+		factoryBeanDefinition.setAttribute(FactoryBean.OBJECT_TYPE_ATTRIBUTE, SomeInterface.class.getName());
+		context.registerBeanDefinition("beanToBeMocked", factoryBeanDefinition);
+		context.register(MockedFactoryBean.class);
+		context.refresh();
+		assertThat(Mockito.mockingDetails(context.getBean("beanToBeMocked")).isMock()).isTrue();
+	}
+
 	@Test
 	void canMockBeanProducedByFactoryBeanWithClassObjectTypeAttribute() {
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();