Update further to ipykernel comm refactoring

[echarles]

This aims to fix the reported failing test on https://github.com/jupyter/notebook/runs/5984992147?check_suite_focus=true

It just changes the needed imports to fit the latest and correct ipykernel package.

FAIL failed_restart: 3 events were triggered
#    type: assertEquals
#    file: /home/runner/work/notebook/notebook/notebook/tests/services/kernel.js
#    subject: 0
#    expected: 3
Test file: /home/runner/work/notebook/notebook/notebook/tests/services/serialize.js
PASS Created echo comm target
FAIL Error running cell:
---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
Input In [1], in <cell line: 2>()
```

[echarles]

@blink1073 This produces more successful tests on the CI.

[blink1073]

Thanks!

[echarles]

Thx @blink1073