[Cashtab] Add an info log on the NFT listings page

Summary: This is just useful to know. Doesn't really make sense to put it in the UX, but convenient to be able to check this in Cashtab.

Test Plan:
npm test, see screenshot

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D16848