Default Payments publisherURL protocol to http://

[ayumi]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Fix #3751

This isn't an ideal solution, but it bandaids #3751 such that publisher links on the Payments page always work.
In the future we might revisit the intermittently missing ledgerInfo favicon / protocol.

Auditors: @mrose17

Test Plan:

1. Browse various websites for >8s each
2. Check Preferences -> Payments and confirm that favicon-less publisher links work