jovian: do not marshal new fields in `rollupConfig.Genesis.SytemConfig` until Jovian is active

This is breaking some zk stacks:

> op-succinct and kailua uses the rollup configuration as a commitment hashing that so a new field change the public inputs for zk proving. they use alloy libraries/kona to deserialize the response by op-node for rollup_config, theres a new field, deserialization fails (because strict checks on field do to the hasing/commitment usage), they stop to operate. so existing kona instances will fail on reaching out op-node. and upgrade is not immediate theres a chain of stuff op-node => kona => any other stuff on top.

This needs to be fixed before Fusaka activates on Mainnet.