Update ducc0 minimum requirement to 0.33 and update to ducc0.sht stable API - #536

• Upstream ducc0 sht functions are available in ducc0.sht since 0.33.
• Proposing to update to the stable API and bump ducc0 minimum version requirement to 0.33.

P.S. I am splitting out changes from my Clenshaw-Curtis grid PR so they are easier to manage.

Validation

• make -C examples/python -f Makefile no-timing passes.

Reminders

• Base all changes on the develop branch: the master branch is used only when releasing new versions.
• Run make check to ensure that the python code follows standard formatting conventions.
• If adding new features, update the docstring to provide all information that is required to use the feature.