README: Link to adapters goes to old repo "Jupiter"

[shannonwells]

Summary

In the top-level README, there is a link, "adapters" that points to Jupiter and not the Celestia directory inside sovereign-sdk.

Steps to reproduce

1. View the link

and be compatible with any DA layer - so deploying their rollup on a new chain is as simple as
picking an [adapter](https://github.com/Sovereign-Labs/Jupiter)

The README in that repo directs you to https://github.com/Sovereign-Labs/sovereign-sdk/tree/stable/adapters/celestia

It just needs to be updated to reflect the new location inside this repo.