Fix asyncio.Task type for python<=3.8

[davidbrochart]

Fixes #142

[github-actions]

👈 Launch a Binder on branch davidbrochart/jupyter_collaboration/task_type

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (fd7ec7c) 0.00% compared to head (c50d910) 0.00%.

❗ Current head c50d910 differs from pull request most recent head 02476fd. Consider uploading reports for the commit 02476fd to get more accurate results

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #143   +/-   ##
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  Coverage   0.00%   0.00%           
=====================================
  Files          7       7           
  Lines        452     453    +1     
=====================================
- Misses       452     453    +1     

Impacted Files	Coverage Δ
jupyter_collaboration/handlers.py	0.00% <0.00%> (ø)

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[fcollonval]

Thanks @davidbrochart