Upgrade to React Router 6.11.2

[david-crespo]

This should be trivial, but it's not because:

1. They rewrote how scroll restore works a bit, so our patch letting us restore scroll on something other than window needed to be rewritten
2. I wanted to use a ref instead of an ID, following Allow scrolling of individual elements remix-run/react-router#10468, which is itself rework of my PR useElementScrollRestoration remix-run/react-router#9573
3. I wanted to investigate Scroll restoration on back nav no longer works #1372, which is still a problem