Relax piecewise test tolerances due to upstream changes

[jsiirola]

Fixes # .

Summary/Motivation:

Tests have started failing due to minor changes upstream. This PR relaxes some test tolerances so things pass again.

Changes proposed in this PR:

• relax test tolerances in nonlinear transform.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.41%. Comparing base (a079b25) to head (c712909).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3805   +/-   ##
=======================================
  Coverage   89.41%   89.41%           
=======================================
  Files         909      909           
  Lines      105579   105579           
=======================================
+ Hits        94407    94408    +1     
+ Misses      11172    11171    -1     

Flag	Coverage Δ
builders	29.10% <ø> (-0.02%)	⬇️
default	86.04% <ø> (?)
expensive	35.76% <ø> (?)
linux	86.73% <ø> (-2.46%)	⬇️
linux_other	86.73% <ø> (+<0.01%)	⬆️
osx	82.88% <ø> (ø)
win	84.98% <ø> (ø)
win_other	84.98% <ø> (ø)

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