Remove tox version limit

[Nusnus]

This reverts #8443.
tox v4.11 now works normally.
We're potentially now dependent on 4.11> but I'll leave it without restrictions for now.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (dabccf0) 87.42% compared to head (07c4961) 87.42%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8464   +/-   ##
=======================================
  Coverage   87.42%   87.42%           
=======================================
  Files         148      148           
  Lines       18488    18488           
  Branches     3155     3155           
=======================================
  Hits        16164    16164           
  Misses       2034     2034           
  Partials      290      290           

Flag	Coverage Δ
unittests	87.39% <ø> (ø)

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[Nusnus]

Code cov is failing again.. I'll let it breathe a bit and try again.