Fix issues related to post processing SCHISM results

[SorooshMani-NOAA]

• Fix the inverted condition for combine elev timeseries

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 21.29%. Comparing base (1fbaf14) to head (6d5c14e).
Report is 13 commits behind head on main.

Files	Patch %	Lines
ensembleperturbation/parsing/schism.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #126   +/-   ##
=======================================
  Coverage   21.29%   21.29%           
=======================================
  Files          28       28           
  Lines        3762     3762           
=======================================
  Hits          801      801           
  Misses       2961     2961           

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