fix: SinglePhaseWell Separator flash

[tjb-ltk]

Well separator used for constraint properties did not supply temperature when calling flash

[tjb-ltk]

@dkachuma

Should the fluid model interface should throw if being called when model is thermal ???

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.87%. Comparing base (2b691d5) to head (88665f1).

Files with missing lines	Patch %	Lines
...physicsSolvers/fluidFlow/wells/SinglePhaseWell.cpp	83.33%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3978      +/-   ##
===========================================
- Coverage    58.87%   58.87%   -0.01%     
===========================================
  Files         1356     1356              
  Lines       113234   113243       +9     
===========================================
  Hits         66668    66668              
- Misses       46566    46575       +9     

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