[3.11] gh-104049: do not expose on-disk location from SimpleHTTPRequestHandler (GH-104067) (#104123)

gh-104049: do not expose on-disk location from SimpleHTTPRequestHandler (GH-104067)

Do not expose the local server's on-disk location from `SimpleHTTPRequestHandler` when generating a directory index. (unnecessary information disclosure)

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(cherry picked from commit c7c3a60c88de61a79ded9fdaf6bc6a29da4efb9a)

Co-authored-by: Ethan Furman <ethan@stoneleaf.us>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>