Reference to old redux-devtools-extension

[Timppe]

What docs page needs to be fixed?

https://redux.js.org/usage/configuring-your-store#integrating-the-devtools-extension

What is the problem?

The docs are referring to a deprecated package https://www.npmjs.com/package/redux-devtools-extension

What should be changed to fix the problem?

Docs should refer to https://www.npmjs.com/package/@redux-devtools/extension which the previous package's author recommends to use instead, if this is still in line with the redux core team

[markerikson]

Sure, please file a PR to update this!