Jupyter depends on a greater version of core

[montanalow]

What

Bump the required version of jupyter-core

Why

To resolve this error:

ERROR: After October 2020 you may experience errors when installing or updating packages. This is because pip will change the way that it resolves dependency conflicts.
We recommend you use --use-feature=2020-resolver to test your packages with the new resolver before it becomes the default.
jupyter-client 6.1.7 requires jupyter-core>=4.6.0, but you'll have jupyter-core 4.4.0 which is incompatible.
notebook 6.1.5 requires jupyter-core>=4.6.1, but you'll have jupyter-core 4.4.0 which is incompatible.