Disable colour to fix CI

[hugovk]

The CI started failing like this:

Because the FORCE_COLOR=1 from the workflow is being passed to the tests, and adding colour to the output.

Let's instead disable colour for the affected tests by setting NO_COLOR to True, like we do with another, because colour isn't relevant to these tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (46f649c) 98.97% compared to head (60c1d0b) 98.98%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #190   +/-   ##
=======================================
  Coverage   98.97%   98.98%           
=======================================
  Files           7        7           
  Lines         391      393    +2     
=======================================
+ Hits          387      389    +2     
  Misses          4        4           

Flag	Coverage Δ
macos-latest	98.98% <100.00%> (+<0.01%)	⬆️
ubuntu-latest	98.98% <100.00%> (+<0.01%)	⬆️
windows-latest	98.98% <100.00%> (+<0.01%)	⬆️

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