Update Hilla docs to replace imports from react-router-dom with react-router

[taefi]

With the adoption of React Router 7 in Vaadin 24.7, the documentations should be updated to reflect the same.
There are points in documentations that still import the NavLink, Outlet, useNavigate, useLocation, and etc. from the react-router-dom package.

These are some of the articles (but there might be more):

• https://vaadin.com/docs/latest/hilla/guides/routing
• https://vaadin.com/docs/latest/hilla/guides/from-java-to-react

Note: as Minor versions are also going to be available for the docs, it should be considered that the usage of react-router-dom is fine in 24.6 and older, but not in 24.7+.