Dead link to Arbitrum API

[slrslr]

When you search for "node through Infura" at https://docs.getsession.org/contribute-to-the-session-network/running-a-session-node

then follows a dead link:

https://github.com/search?q=repo%3Asession-foundation%2Fsession-docs%20https%3A%2F%2Fdocs.infura.io%2Fapi%2Fgetting-started&type=code