[Cashtab] Fix SendByUrlParams balance header assertion after XEC ticker move

Summary:
D20334 moved the XEC ticker into the eCash card title, so Balance
XEC text is the amount only. Update the bip21 op_return_raw SendByUrlParams
cases that still expected "9,513.12 XEC".

Test Plan:

• cd cashtab && pnpm test --testPathPatterns=SendByUrlParams --watchAll=false --coverage=false
• cd cashtab && pnpm test --testPathPatterns=Collection/index.test --watchAll=false --coverage=false

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D20343