Add @Override annotations to test sources

Issue: SPR-10129

spring-context/src/test/java/example/scannable/StubFooDao.java

@@ -26,6 +26,7 @@ import org.springframework.stereotype.Repository;
 @Qualifier("testing")
 public class StubFooDao implements FooDao {
 
+	@Override
 	public String findFoo(int id) {
 		return "bar";
 	}