[Docs]: Why install react-router-dom, if next instruction is to uninstall it?

[ChristianVilen]

Describe what's incorrect/missing in the documentation

As seen on this screenshot:

[timdorr]

Because for the vast majority of apps out there, step 1 might be all you need to do. And for those that blindly update deps and check for problems later, we want to demonstrate that this is fine. 7.x is almost a non-breaking change.