fix build when using a private RapidJSON library

[ptahmose]

Description

The CMake-build failed when using a private RapidJSON-library (i.e. when LIBCZI_BUILD_PREFER_EXTERNALPACKAGE_RAPIDJSON would be false) when attempting to clone the repository because when specifying "GIT_SHALLOW TRUE" it is not possible to use a git-hash as tag. C.f. here.
This removes the GIT_SHALLOW specifier, and while at it, switches to the latest version.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

locally

Checklist:

• I followed the Contributing Guidelines.
• I did a self-review.
• I commented my code, particularly in hard-to-understand areas.
• I updated the documentation.
• I updated the version of libCZI following Versioning of libCZI depending on the type of change
  • Bug fix -> PATCH
  • New feature -> MINOR
  • Breaking change -> MAJOR
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.50%. Comparing base (6b0fbc9) to head (f38bd22).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #117   +/-   ##
=======================================
  Coverage   65.50%   65.50%           
=======================================
  Files          86       86           
  Lines       10893    10893           
=======================================
  Hits         7136     7136           
  Misses       3757     3757           

Flag	Coverage Δ
windows-latest	65.50% <ø> (ø)

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