gh-36218: src/bin/sage-env: set PYDEVD_DISABLE_FILE_VALIDATION=1
This fixes a doctest with newer versions of debugpy, as seen in in
https://github.com/sagemath/sage/pull/36141 and
https://github.com/sagemath/sage/pull/36129. Explanation in the commit
message.
URL: https://github.com/sagemath/sage/pull/36218
Reported by: Michael Orlitzky
Reviewer(s): Matthias Köppe
