Remove pin on `jupyter-core<5.8.0`

[jtpio]

Issue to track removing this pin on CI on the 7.4.x branch:

notebook/.github/workflows/build.yml

Lines 160 to 164 in 071d48a

	- name: Temporary pin for jupyter-core on Windows
	if: matrix.os == 'windows-latest'
	run: |
	# See https://github.com/jupyter-server/jupyter_server/issues/1527
	${{ matrix.py_cmd }} -m pip install "jupyter-core<5.8.0"

To be done after jupyter-server/jupyter_server#1527 is fixed in a new jupyter-server release.

[minrk]

jupyter-core 5.8.1 is out now and should fix the problem without any changes to jupyter-server