Update silicon testnet info

[jaybbbb]

Sepolia Testnet

• We reviewed problems together with the Polygon team but couldn’t find a suitable solution, so we will update the testnet setup.
• We will revert to using the deprecated chain and set the currently active chain to inactive.

[github-actions]

You successfully submitted a PR! Due to the amount of PRs coming in: we will only look at PRs that the CI is happy with. We can also not hold your hand getting the CI green - just look how others that where merged did it and RTFM. So as long as there is any CI check that reports an error - no human will look at this. You might be able to ask for some support after supporting the project - e.g. by sending funds to lists.eth. When you fixed things after a requested change - then you also need to (re-)request a review.