Update the RPC endpoints

[rootulp]

Context

https://celestia-team.slack.com/archives/C05KFLSKZFW/p1771815274400139

Problem

A lot of the RPC endpoints no longer work: https://docs.celestia.org/operate/networks/mainnet-beta/#community-consensus-endpoints

Proposal

1. [one time] Update the list to contain only active endpoints. We can use a tool like https://celestia-tools.brightlystake.com/ to test which ones are active or inactive
2. [optional][recurring] set up CI to auto update the list with only active endpoints