fix: prysm config

[gzeoneth]

Need to change or otherwise testnode fail to start with --pos with

nitro-testnode-create_beacon_chain_genesis-1  | time="2024-08-15T05:44:28Z" level=fatal msg="Could not generate beacon chain genesis state" error="could not set config params: version 0x03000000 for fork capella in config interop conflicts with existing config named=mainnet: configset cannot add config with conflicting fork version schedule" prefix=genesis

This should work now, also reduced slot time to 2 seconds so test deployment would go faster.

[tsahee]

LGTM