convert unsafe fs::path std::string conversion call
convert unsafe fs::path std::string conversion call

Summary: This one was introduced due to out of order backports. It should have been removed in D10798.

Test Plan: `ninja all check-all`

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D11972

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