Revert "setup.py: Pin werkzeug<2.1"
Revert "setup.py: Pin werkzeug<2.1"

This reverts commit 67021071ec98a7e8f4cb81cc9a3af0e20458e20f.

Reason for revert: Since 9d85d02f8d22b1d2a889bf6add49ecc5a3ade717
"utils: hash: Use hashlib for pbkdf2", Isso is compatible
with (yet-to-be-released) `werkzeug>=2.1`, so we have no
reason to pin the version any longer.

posativ/isso,posativ/isso,posativ/isso,posativ/isso