Update rapidjson to latest

[darbyjohnston]

This PR updates the rapidjson dependency to the latest changes. This replaces the previous dependabot PR. Note that rapidjson doesn't seem to use git tags for versioning (the last tag is from 2016).

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.00%. Comparing base (c0e97b0) to head (4c4daea).
⚠️ Report is 70 commits behind head on main.

❌ Your changes status has failed because you have indirect coverage changes. Learn more about Unexpected Coverage Changes and reasons for indirect coverage changes.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1943      +/-   ##
==========================================
+ Coverage   84.11%   85.00%   +0.88%     
==========================================
  Files         198      181      -17     
  Lines       22241    13074    -9167     
  Branches     4687     1206    -3481     
==========================================
- Hits        18709    11113    -7596     
+ Misses       2610     1778     -832     
+ Partials      922      183     -739     

Flag	Coverage Δ
py-unittests	85.00% <ø> (+0.88%)	⬆️

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see 139 files with indirect coverage changes

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