Remove [[some!]] unused variables

[sbryngelson]

This PR removes some unused variables.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 43.03%. Comparing base (6bad379) to head (969b8d3).
Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
src/simulation/m_data_output.fpp	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #699      +/-   ##
==========================================
+ Coverage   42.99%   43.03%   +0.04%     
==========================================
  Files          61       61              
  Lines       16053    16058       +5     
  Branches     1796     1797       +1     
==========================================
+ Hits         6902     6911       +9     
+ Misses       8167     8157      -10     
- Partials      984      990       +6     

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