[PR #9326/fe26ae2 backport][3.10] Fix TimerContext not uncancelling the current task

[bdraco]

(cherry picked from commit fe26ae2)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.79%. Comparing base (52e0b91) to head (2d9964c).
Report is 1 commits behind head on 3.10.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             3.10    #9328   +/-   ##
=======================================
  Coverage   97.79%   97.79%           
=======================================
  Files         108      108           
  Lines       34842    34885   +43     
  Branches     4163     4173   +10     
=======================================
+ Hits        34072    34115   +43     
  Misses        573      573           
  Partials      197      197           

Flag	Coverage Δ
CI-GHA	97.68% <95.65%> (-0.01%)	⬇️
OS-Linux	97.36% <95.65%> (-0.01%)	⬇️
OS-Windows	94.97% <95.65%> (+<0.01%)	⬆️
OS-macOS	97.06% <95.65%> (-0.01%)	⬇️
Py-3.10.11	96.92% <21.73%> (-0.10%)	⬇️
Py-3.10.15	96.86% <21.73%> (-0.10%)	⬇️
Py-3.11.10	96.94% <95.65%> (-0.01%)	⬇️
Py-3.11.9	97.01% <95.65%> (+<0.01%)	⬆️
Py-3.12.6	97.40% <95.65%> (-0.01%)	⬇️
Py-3.13.0-rc.2	97.39% <95.65%> (-0.01%)	⬇️
Py-3.8.10	94.37% <21.73%> (-0.11%)	⬇️
Py-3.8.18	96.66% <21.73%> (-0.10%)	⬇️
Py-3.9.13	96.84% <21.73%> (-0.10%)	⬇️
Py-3.9.20	96.78% <21.73%> (-0.10%)	⬇️
Py-pypy7.3.16	96.38% <21.73%> (-0.10%)	⬇️
VM-macos	97.06% <95.65%> (-0.01%)	⬇️
VM-ubuntu	97.36% <95.65%> (-0.01%)	⬇️
VM-windows	94.97% <95.65%> (+<0.01%)	⬆️

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