docs: update with Filecoin mainnet, remove ETH Goerli

[dtbuchholz]

Summary

Mentions of Filecoin Mainnet being unsupported have been removed. There was also a mention of an ETH Goerli heltbot table instead of Sepolia.

Context

N/A

Implementation overview

N/A

Implementation details and review orientation

N/A

Checklist

• [x] Are changes backward compatible with existing SDKs, or is there a plan to manage it correctly?
• [x] Are changes covered by existing tests, or were new tests included?
• [x] Are code changes optimized for future code readers, commenting on problematic areas to understand (if any)?
• [x] Future-self question: Did you avoid unjustified/unnecessary complexity to achieve the goal?

[dtbuchholz]

Note: it looks like staging doesn't have all of the changes currently in main, so I'm pointing to main here. Lmk if I should adjust that.

[avichalp]

@dtbuchholz: looks good!, i have one small question. its seems okay to merge directly in the main after the staging is merged since it is a small change in the docs imo

[dtbuchholz]

cool, sgtm. i can wait til that happens and then merge this to main