don't prevent users from using newer versions of psutil

[ctcjab]

pyproject.toml currently specifies psutil~=5.6:

jupyter-resource-usage/pyproject.toml

Line 41 in 97f8708

"psutil~=5.6",

This is preventing users from picking up newer versions of psutil. Lots of bugfixes have been released since the 5.6 series.

See https://iscinumpy.dev/post/bound-version-constraints/ for why it is not good practice to propagate this upper bound to your users.