Switch back to using the upstream @walletconnect/universal-provider

We added our custom version to work-around the "WalletConnect signing out on every transaction" issue in #250.

The upstream fixed it in https://github.com/WalletConnect/walletconnect-monorepo/pull/6866 and released it as part of [@walletconnect/universal-provider version 2.21.9](https://github.com/WalletConnect/walletconnect-monorepo/releases/tag/%40walletconnect%2Funiversal-provider%402.21.9).