Fix shipping_method_spec test flakiness

[DianeLooney]

Checking collection equality with eq can flake depending on the order of
items in the collection. Instead, using match_array allows for out of
order items.

Manually testing a second matcher with the collection .reversed gives a 100% fail rate. Changing the assertion to a match_array gives a 100% pass rate.

Checklist:

• I have followed Pull Request guidelines
• I have added a detailed description into each commit message
• I have updated Guides and README accordingly to this change (if needed)
• I have added tests to cover this change (if needed)
• I have attached screenshots to this PR for visual changes (if needed)

[spaghetticode]

Thanks!