fix(functional-test): update failing coupon tests

[sardesam]

Because

• We are aiming to make stage and prod deployments all green.
• There is still flakiness.

This pull request

• Updates tests to add a longer timeout to page locators.
• Follow up to fix(functional-test): update failing coupon tests #16983.

Issue that this pull request solves

Closes FXA-9689

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).

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