Remove third party library rapidjson

[Bai-Li-NOAA]

What is the feature?

This PR addresses issue #391. We created a inst/include/utilities/fims_json.hpp as a file parser but did not delete the third library file parser from the codebase.

How have you implemented the solution?

Deleted the tests/integration/third_party/ folder

Does the PR impact any other area of the project?

No

How to test this change

All GHA checks have passed.

Developer pre-PR checklist

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[github-actions]

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Checklist

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (de543db) 74.58% compared to head (ebde74d) 76.10%.

❗ Current head ebde74d differs from pull request most recent head 74e0a07. Consider uploading reports for the commit 74e0a07 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #519      +/-   ##
==========================================
+ Coverage   74.58%   76.10%   +1.52%     
==========================================
  Files          38       37       -1     
  Lines        2034     1791     -243     
  Branches      136        0     -136     
==========================================
- Hits         1517     1363     -154     
+ Misses        476      428      -48     
+ Partials       41        0      -41     

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