Clean up app/code/Magento/AdvancedPricingImportExport/Test/Unit/Model/Import/AdvancedPricing/Validator/WebsiteTest.php

[dmanners]

Preconditions (*)

1. 2.3-develop
2. PHPStan installed

Steps to reproduce (*)

1. Run ./vendor/bin/phpstan analyse app/code/Magento/AdvancedPricingImportExport/Test/Unit/Model/Import/AdvancedPricing/Validator/WebsiteTest.php

Expected result (*)

1. No Errors

Actual result (*)

 1/1 [▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓] 100%

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  Line   WebsiteTest.php                                                                                                                                                                     
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  106    Access to an undefined property Magento\AdvancedPricingImportExport\Test\Unit\Model\Import\AdvancedPricing\Validator\WebsiteTest::$websiteString.                                   
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 [ERROR] Found 1 error