Chore (ui-shared-deps): Clean up direct usage of OUI theme JSON

[joshuarrrr]

Description

As part of #5652, I looked into the various ways we consume OUI themes. One thing I realized is that, when using the JSON files to fetch SASS variables, we should always do it via ui-shared-deps, which is dark/light-mode aware. This change fixes the imports, although further refactoring is deferred to the linked issue: #5661

Issues Resolved

Screenshot

Testing the changes

Check List

• All tests pass
  • yarn test:jest
  • yarn test:jest_integration
• New functionality includes testing.
• New functionality has been documented.
• Update CHANGELOG.md
• Commits are signed per the DCO using --signoff

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (6710ec3) 67.02% compared to head (ddd084f) 67.02%.
Report is 5 commits behind head on main.

Files	Patch %	Lines
...s/expressions/public/react_expression_renderer.tsx	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5662      +/-   ##
==========================================
- Coverage   67.02%   67.02%   -0.01%     
==========================================
  Files        3294     3294              
  Lines       63309    63309              
  Branches    10071    10071              
==========================================
- Hits        42435    42433       -2     
- Misses      18430    18431       +1     
- Partials     2444     2445       +1     

Flag	Coverage Δ
Linux_1	35.24% <75.00%> (ø)
Linux_2	55.19% <ø> (ø)
Linux_3	43.86% <0.00%> (-0.01%)	⬇️
Linux_4	35.34% <0.00%> (ø)
Windows_1	35.26% <75.00%> (ø)
Windows_2	55.15% <ø> (ø)
Windows_3	43.88% <0.00%> (ø)
Windows_4	35.34% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.