fix(usps): remove duplicate <price_type> node breaking config XML merge (#40779)

[lbajsarowicz]

Description

app/code/Magento/Usps/etc/config.xml shipped two sibling <price_type> nodes
(EPS and COMMERCIAL) under <carriers><usps>. Magento's Dom config reader
rejects sibling elements with the same tag name and throws
More than one node matching the query: /config/default/carriers/usps/price_type
during any config merge (any custom module overriding a USPS carrier value
triggers it, as does bin/magento cache:clean).

EPS is not a valid price_type value — the dropdown source
(Magento\Usps\Model\Config\Source\PriceType) only exposes COMMERCIAL
and RETAIL; EPS is an account type. Kept the canonical
COMMERCIAL default.

Fixes #40779

Fixed Issues

• Fixes Duplicate <price_type> node in quality patch AC-15210 breaks config XML merge #40779: Duplicate <price_type> node in quality patch AC-15210 breaks config XML merge

Manual testing scenarios

1. Create a custom module overriding <carriers><usps><price_type> in etc/config.xml.
2. Run bin/magento cache:clean.
3. Before this fix: main.ERROR: More than one node matching the query: /config/default/carriers/usps/price_type. After: cache clears cleanly.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (106 USPS unit tests pass)
• Changes to the codebase comply with technical guidelines

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[lbajsarowicz]

@magento run all tests