Update papermill.cli references to papermill per 2.3.4 release

[speediedan]

🐛 Bug

With the latest papermill release (2.3.4, updated 2022.01.22), a PR has been included that necessitates a change in our papermill.cli references to papermill

To Reproduce

As part of the make ipynb process, you'll notice python -m papermill.cli {ipynb_file} {pub_ipynb} --kernel python fails. Updating it to python -m papermill {ipynb_file} {pub_ipynb} --kernel python succeeds. In the PR I'm submitting to fix this, I'm also updating requirements to ensure papermill >=2.3.4 as previously, papermill.cli was necessary.

Expected behavior

make ipynb process should generate the relevant executed notebooks

Additional context

The improvement to papermill was originally made by @Borda and now is finally available. Thanks!