fix(docs): icons in docs not rendered properly

[lucivpav]

This PR updates the outdated code snippets in theming section of docs. The icon colors were not set properly and the output did not match user's expectation. Relevant issue with error description: #1591.

Before:

After:

[codecov]

Codecov Report

Merging #1625 into master will decrease coverage by 0.2%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1625      +/-   ##
==========================================
- Coverage   71.49%   71.28%   -0.21%     
==========================================
  Files         846      846              
  Lines        6945     6938       -7     
  Branches     2002     1982      -20     
==========================================
- Hits         4965     4946      -19     
- Misses       1974     1986      +12     
  Partials        6        6

Impacted Files	Coverage Δ
...ages/react/test/specs/behaviors/testDefinitions.ts	87.39% <0%> (-5.58%)	⬇️
...b/accessibility/Behaviors/Tree/treeItemBehavior.ts	100% <0%> (ø)	⬆️
packages/react/src/components/Tree/TreeItem.tsx	76.31% <0%> (+1.31%)	⬆️

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@a5ff320). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1625   +/-   ##
=========================================
  Coverage          ?   70.07%           
=========================================
  Files             ?      867           
  Lines             ?     7429           
  Branches          ?     2161           
=========================================
  Hits              ?     5206           
  Misses            ?     2215           
  Partials          ?        8

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[lucivpav]

This was fixed by PR #1764. Closing this as it is no longer relevant.