Fix Untrusted search path under some conditions on Windows allows arbitrary code execution

[imhunterand]

Although GitPython often avoids executing programs found in an untrusted search path since 3.1.33, two situations remain where this still occurs. Either can allow arbitrary code execution under some circumstances.

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[mjwolf]

Hi @imhunterand, thanks for the contribution, but the same change has already been merged with #2313, so this PR is no longer needed