Remove zend json from weee

[dmanners]

Description

Since Zend Framework 1 is at end of life we should remove the usage of Zend_Json. This review is part of #9236

Fixed Issues (if relevant)

1. Upgrade ZF components. Zend_Json #9236: Upgrade ZF components. Zend_Json (Part fix)

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[dmanners]

I was seeing issues with some test cases under /Magento/Weee/Test/Unit/Model/Attribute/Backend/Weee/TaxTest.php it seems that

magento2/app/code/Magento/Catalog/Model/Product/Attribute/Backend/Price.php

Line 77 in 99e85cb

$this->scopeOverriddenValue = $scopeOverriddenValue

is causing issues as this is the tax model's parent but the tax model does not deal with the attribute ScopeOverriddenValue

[okorshenko]

@dmanners thank you for reporting about Magento/Weee/Test/Unit/Model/Attribute/Backend/Weee/TaxTest.php. We will fix it

[magento-team]

@dmanners thank you for your contribution to Magento 2 project