unregister phar only when appropriate

[adaudenthun]

Calling stream_wrapper_unregister('phar') without checking if it's registered will trigger a warning

Link issue : #21973

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[adaudenthun]

@magento-engcom-team give me test instance

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[magento-engcom-team]

Hi @orlangur, thank you for the review.
ENGCOM-4681 has been created to process this Pull Request

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