ci: rename "trial" tox factor to "twisted"

[blueyed]

Ref: #4848 (comment)

[codecov]

Codecov Report

Merging #4963 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4963      +/-   ##
==========================================
+ Coverage   95.68%   95.71%   +0.02%     
==========================================
  Files         113      113              
  Lines       25178    25178              
  Branches     2498     2498              
==========================================
+ Hits        24091    24098       +7     
+ Misses        766      764       -2     
+ Partials      321      316       -5

Impacted Files	Coverage Δ
src/_pytest/terminal.py	91.74% <0%> (+0.82%)	⬆️
src/_pytest/cacheprovider.py	97.16% <0%> (+0.94%)	⬆️

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[nicoddemus]

I don't believe we need a CHANGELOG btw

[blueyed]

JFI: Azure failed (https://pytest-dev.visualstudio.com/pytest/_build/results?buildId=497&view=results):

Could not retrieve file content for /azure-pipelines.yml from repository self hosted on https://api.github.com using commit dddbd38. GitHub reported the error, "Maximum threads for service reached"

Could not restart it, since my account has been suspended?!
Pushed a new commit.