Update web3-react connector to support web3-react v8

[mmv08]

Overview

web3-react delivered v8 recently. From this version they also include a Safe conector that already includes the SDK integration.

• Should update the readme to make clear that our web3-react package is only valid up to v6.
• Should deprecate the package and point to the one included by default instead.

Bonus

• Test with our Test App that web3-react v8 is working as expected with the Safe