chore!: remove DAppKit

[jeanregisser]

Description

It's time to say good bye to DAppKit! We thank you for being the very first way to interact with DApps on Celo.

• DAppKit has been sunset since march 2023
  • https://forum.celo.org/t/sunsetting-dappkit/5336
• no dapps on the dapps list are actively using it

Test plan

• Tests pass

Related issues

• Fixes RET-853
• Fixes ACT-1101
• Fixes ACT-1088

Backwards compatibility

No, but nobody's using DAppKit anymore.

Network scalability

If a new NetworkId and/or Network are added in the future, the changes in this PR will:

• [x] Continue to work without code changes, OR trigger a compilation error (guaranteeing we find it when a new network is added)