[Cashtab] Fix bug in agora tx parsing

Summary:
When I patched "we have to look at all the inputs to find the p2sh" -- I was still checking only the inputs[0] input script.

Fix.

Test Plan: npm test (confirms txs are parsed correctly)

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D17014