Uncancel tasks after timeout in python 3.11

[tristan]

What do these changes do?

Python 3.11 introduced the concept of uncancelling a cancelled task.
From https://docs.python.org/3/library/asyncio-task.html#task-cancellation

user code should not generally call uncancel. However, in cases when suppressing asyncio.CancelledError is truly desired, it is necessary to also call uncancel() to completely remove the cancellation state.

This updates async-timeout to be compliant with python 3.11 when cancelling the tasks after a timeout

Are there changes in behavior for the user?

no

Related issue number

#362

Checklist

• I think the code is well written

• but happy to receive change suggestions!

• Unit tests for the changes exist
• Documentation reflects the changes
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> (e.g. 588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the PR
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: Fix issue with non-ascii contents in doctest text files.

[codecov]

Codecov Report

Merging #363 (1cb6f25) into master (adf9e28) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #363   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          105       116   +11     
  Branches        18        19    +1     
=========================================
+ Hits           105       116   +11     

Flag	Coverage Δ
unit	98.27% <94.11%> (-0.78%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
async_timeout/__init__.py	100.00% <100.00%> (ø)

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