chore: fix 404 link in readme (#21136)

Author: ZheSun88

README.md

@@ -2,7 +2,7 @@ Vaadin Flow
 ======
 *[Vaadin Flow](https://vaadin.com/flow) is the Java framework of Vaadin Platform for building modern websites that look great, perform well and make you and your users happy.*
 
-**For instructions about developing web applications with Vaadin Flow**, please refer to [the documentation](https://vaadin.com/docs/latest/flow/overview).
+**For instructions about developing web applications with Vaadin Flow**, please refer to [the documentation](https://vaadin.com/docs/latest/flow).
 
 **To contribute, first refer to [Contribution Guide](/CONTRIBUTING.md) for general instructions and requirements for contributing code to Flow.**