Fixes error pointed out by Jinliang in SOC interpolation function

[dallan-keylogic]

Fixes

Switches evaluation indexes in interpolation function used in SOC submodels

Summary/Motivation:

The original interpolation function had a typo, this PR fixes it. However, I don't believe it should affect anything we've published, because the incorrect formula gives the correct answer when a uniform discretization is used.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (690eb5e) 77.41% compared to head (5401f33) 77.40%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1314      +/-   ##
==========================================
- Coverage   77.41%   77.40%   -0.01%     
==========================================
  Files         390      390              
  Lines       63631    63631              
  Branches    11702    11702              
==========================================
- Hits        49258    49255       -3     
- Misses      11835    11839       +4     
+ Partials     2538     2537       -1     

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[lbianchi-lbl]

@AlexNoring @NishantGiridhar would you be able to review this soon?

[AlexNoring]

lgtm

[NishantGiridhar]

LGTM

[lbianchi-lbl]

@dallan-keylogic I'll merge this after resolving the (new) failures that are happening because of #1317.