devel/py-flufl.i18n: fix stage

staging still breaks because PEP517_INSTALL_CMD and USE_PYTHON=autoplist
do not handle the period (.) name normalisation bit that hatchling
implements properly. For now, use a hack that allows correct packaging
until PR 270358/review D46236 is committed, at which point the hack
becomes a no-op.

Pointy-hat to: vishwin
With hat: python
PR: 293773