SpecID not updated when modify_spec_id

[publicqi]

https://github.com/bluealloy/revm/blob/main/crates/revm/src/handler.rs#L185-L199

    pub fn modify_spec_id(&mut self, spec_id: SpecId) {
        if self.cfg.spec_id == spec_id {
            return;
        }

        let registers = core::mem::take(&mut self.registers);
        // register for optimism is added as a register, so we need to create mainnet handler here.
        let mut handler = Handler::mainnet_with_spec(spec_id);
        // apply all registers to default handeler and raw mainnet instruction table.
        for register in registers {
            handler.append_handler_register(register)
        }
        handler.cfg = self.cfg();
        *self = handler;
    }

Although the handler's behavior is updated, the cfg is still the old one with old SpecID.