Update Solution.equilibrate()'s docstring with NativeEOS.equilibrate() docstring

[SuixiongTay]

Summary

• Minor docstring update by copying the updated docstring of NativeEOS.equilibrate() to Solution.equilibrate()
• Addressing Copy the updated docstring of NativeEOS.equilibrate to Solution.equilibrate #343

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.42%. Comparing base (869084e) to head (541c6db).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #344   +/-   ##
=======================================
  Coverage   86.42%   86.42%           
=======================================
  Files          14       14           
  Lines        1856     1856           
  Branches      322      322           
=======================================
  Hits         1604     1604           
  Misses        207      207           
  Partials       45       45           

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[rkingsbury]

Thank you @SuixiongTay !