Fix `zombienet-polkadot-functional-spam-statement-distribution-requests`

@AndreiEres
This tests occasionally fails. Example:
https://github.com/paritytech/polkadot-sdk/actions/runs/15669788401/job/44138943418

Could you take a look?

Originally posted in https://github.com/paritytech/polkadot-sdk/pull/8748 [here](https://github.com/paritytech/polkadot-sdk/pull/8748/files/5b7beef15ef968ade2b88cf078e3f172c94bb0cf#r2149746692)