fix(iota): caip2 prescribes a JSON-RPC method that does not exist

[okwme]

The iota CAIP-2 profile tells implementers to resolve the chain identifier with iotax_getChainIdentifier. That method returns -32601 Method not found on IOTA mainnet.

The working method is iota_getChainIdentifier, and it returns 6364aad5 — exactly the identifier this profile already documents in its own text and test cases.

Verified against https://api.mainnet.iota.cafe on 2026-09-14:

$ curl -s -X POST https://api.mainnet.iota.cafe -H "Content-Type: application/json" \
    -d "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"iotax_getChainIdentifier\",\"params\":[]}"
{"jsonrpc":"2.0","id":1,"error":{"code":-32601,"message":"Method not found"}}

$ curl -s -X POST https://api.mainnet.iota.cafe -H "Content-Type: application/json" \
    -d "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"iota_getChainIdentifier\",\"params\":[]}"
{"jsonrpc":"2.0","id":1,"result":"6364aad5"}

So an implementer following the profile as written cannot resolve the identifier it specifies. Three occurrences updated; nothing else changed.

Found while writing a CAIP-19 asset profile for this namespace, as part of FAR, an open cross-reference between CAIP-19, CoinGecko and ISO 24165 identifiers. Happy to adjust the wording if the editors prefer a different form.