Use trio.CancelScope instead of deprecated trio.open_cancel_scope

[rnovatorov]

Fixes corresponding TrioDeprecationWarning.

[codecov]

Codecov Report

Merging #80 into master will decrease coverage by 0.22%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #80      +/-   ##
==========================================
- Coverage   99.78%   99.56%   -0.23%     
==========================================
  Files          19       19              
  Lines         476      461      -15     
  Branches       41       43       +2     
==========================================
- Hits          475      459      -16     
- Misses          1        2       +1

Impacted Files	Coverage Δ
pytest_trio/_tests/test_fixture_ordering.py	100% <ø> (ø)	⬆️
pytest_trio/plugin.py	98.94% <100%> (-0.54%)	⬇️
pytest_trio/_tests/test_hypothesis_interaction.py	100% <0%> (ø)	⬆️

[Zac-HD]

Closed by #73.

[njsmith]

Oh whoops, it looks like #73 included these fixes already, so now that I updated the PR by merging from master, the changes tab is now totally empty. Guess that means we can close this... thank you though, it was a good PR :-).

We should do a release...