Fixed typo in TaxRuleRepositoryTest class.

[dverkade]

Description

This PR fixes a typo in the TaxRuleRepositoryTest class and changed the method name because the "If" was missing in the name of the method.

Since it's a test we can rename the method without deprecating it.

[magento-engcom-team]

Hi @dverkade. Thank you for your contribution
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[sidolov]

Hi @dverkade , unfortunately, we can't accept such Pull Requests to 2.2 release line, all code cleanup like typos, spelling mistakes, etc should be delivered to 2.3 release line. For more information, please, refer to Magento Code Contributions Guide

[dverkade]

I have created a PR for Magento 2.3 here: #17293