fix: don't import scss vars from brand package

[brian-smith-tcril]

Description

We shouldn't be importing this from @edx/brand. Paragon's utilities-only.scss imports variables. Paragon's _variables.scss ensures the scss variables in this file compile to read css variables. Brand packages provide css variables.

[adamstankiewicz]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.89%. Comparing base (d775096) to head (435cecd).
Report is 2 commits behind head on master-design-tokens.

Additional details and impacted files

@@                  Coverage Diff                   @@
##           master-design-tokens    #2026    +/-   ##
======================================================
  Coverage                 93.89%   93.89%            
======================================================
  Files                      1154     1154            
  Lines                     24061    24061            
  Branches                   5200     5096   -104     
======================================================
  Hits                      22592    22592            
  Misses                     1401     1401            
  Partials                     68       68            

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