move bepolia config to the sepolia repository

[q9f]

if nobody disagrees, I would like to move the prater config to the stand-alone goerli repository:

• https://github.com/eth-clients/sepolia (formerly https://github.com/goerli/sepolia)

the rationale is that the merge is not only technical but also logical. also, long-standing testnets should have their dedicated home.

edit: here https://github.com/eth-clients/sepolia/tree/main/bepolia

[arnetheduck]

sgtm!