Fix minor typo: taht -> that in set.py

[skeept]

Fixes # .

Summary/Motivation:

Changes proposed in this PR:

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[codecov]

Codecov Report

Base: 87.06% // Head: 87.05% // Decreases project coverage by -0.00% ⚠️

Coverage data is based on head (0abb549) compared to base (2e01eb7).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2679      +/-   ##
==========================================
- Coverage   87.06%   87.05%   -0.01%     
==========================================
  Files         757      757              
  Lines       84448    84448              
==========================================
- Hits        73521    73517       -4     
- Misses      10927    10931       +4     

Flag	Coverage Δ
linux	84.49% <ø> (-0.01%)	⬇️
osx	74.53% <ø> (ø)
other	84.68% <ø> (ø)
win	81.82% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pyomo/core/base/set.py	99.72% <ø> (ø)
pyomo/contrib/mindtpy/iterate.py	79.54% <0.00%> (-1.82%)	⬇️

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