Typo in payment credit error message

Problem/Motivation

Missing "l" in "settled" in this error message:

    Credit failed: The referenced transaction does not meet the criteria for issuing a credit.
    The transaction must be setted before a credit can be issued. This usually takes 24 hours

Steps to reproduce

Try to issue a credit on a pending payment (/admin/commerce/orders/NNNNN/payment).

Proposed resolution

Fix the misspelled word. Patch coming.

Remaining tasks

Review, commit.

User interface changes

Pedants rejoice.

API changes

None.

Data model changes

None.