Remove initial_guess_w_SS from default parameters

[jdebacker]

This PR removes initial_guess_w_SS from default params per suggestions in OG-Core Issue PSLmodels/OG-Core#1039.

Note that once OG-Core is updated with PSLmodels/OG-Core#1042, OG-PHL will break without this change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.65%. Comparing base (cfaf247) to head (4d37415).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #43   +/-   ##
=======================================
  Coverage   70.65%   70.65%           
=======================================
  Files          12       12           
  Lines         276      276           
=======================================
  Hits          195      195           
  Misses         81       81           

Flag	Coverage Δ
unittests	70.65% <100.00%> (ø)

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[SeaCelo]

Merging