devel/py-importlib-metadata: Update 4.8.1 → 6.0.0

Remove upper limitation on version in devel/py-poetry because it
doesn't change tests outcome.

This unbreaks devel/py-jupyterlab and also opens path for several
other ports that depend on the newest devel/py-importlib-metadata
versions.

PR: 269125
Approved by: portmgr (unbreak devel/py-jupyterlab)