Remove unused function CallSpec2.setall

[blueyed]

Fixes #5253.

[codecov]

Codecov Report

Merging #5716 into features will increase coverage by 0.09%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           features    #5716      +/-   ##
============================================
+ Coverage     96.13%   96.22%   +0.09%     
============================================
  Files           117      117              
  Lines         25884    25873      -11     
  Branches       2496     2492       -4     
============================================
+ Hits          24883    24897      +14     
+ Misses          694      672      -22     
+ Partials        307      304       -3

Impacted Files	Coverage Δ
src/_pytest/python.py	95.51% <ø> (+1.2%)	⬆️
src/_pytest/doctest.py	97.02% <0%> (+2.64%)	⬆️
src/_pytest/assertion/util.py	95.03% <0%> (+2.67%)	⬆️

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