[Cashtab] Reinstate paywall article link

Summary: Reinstating the paywall article links in tx history that was removed in D16513

Test Plan:
npm test
npm start
Find a paywall tx in tx history and ensure the article link takes you directly to the article

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D16553