Remove legacy WT3 data files

[kurbansitterley]

Fixes/Resolves:

Removes old WT3 data files (.csvs) that were buried in the case_studies directory.
Possibly part of #1248 ??

Summary/Motivation:

As far as I can tell, these .csvs were not used in any unit model or example/demonstration. I assume we kept them around just as a reference as we were porting the WT3 models into WaterTAP, but they are not needed anymore so could be confusing to someone poking around the examples folder. Also, based on some of the entries, they appear to be copies of versions I had on my local machine at the time of the merger... I am not sure how that happened. Their purpose for being in the watertap repo is not documented anywhere. Their origin is not documented anywhere. Just a couple of random .csvs floating in the ether...

If ever they are needed again, they are available here: https://github.com/NREL/WaterTAP3

Changes proposed in this PR:

• Removes from WaterTAP old legacy WT3 .csvs that are not used for anything.

Legal Acknowledgement

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1. I agree my contributions are submitted under the license terms described in the LICENSE.txt file at the top level of this directory.
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.01%. Comparing base (271e43b) to head (e907ccf).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1422   +/-   ##
=======================================
  Coverage   94.01%   94.01%           
=======================================
  Files         335      335           
  Lines       35561    35561           
=======================================
  Hits        33431    33431           
  Misses       2130     2130           

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[MarcusHolly]

LGTM - I was not even aware these files existed