Fix PoH V2 evidence display source

[kyrers]

Currently, the code assumes that disputes are cross-chain if no arbitrableChainID is present in the meta evidence, and if so, it sets the query parameter arbitrableChainID to 100 (Gnosis) when determining the source for the iframe.

This works for the PoH V1 iframe because it seems to ignore this query parameter and force a connection, but it doesn't work for the PoH V2 iframe, as it uses the parameter and thus will look for the dispute in the wrong chain.