chore: Removes hard-coded colors from legacy-plugin-chart-sankey

[michael-s-molina]

SUMMARY

Removes hard-coded colors from legacy-plugin-chart-sankey.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

Check that the plugin is very similar to the previous version. We may have color, font, and opacity differences due to theme adjustments.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #19493 (ee1af25) into master (5fed10d) will increase coverage by 0.01%.
The diff coverage is 85.00%.

❗ Current head ee1af25 differs from pull request most recent head 60852fc. Consider uploading reports for the commit 60852fc to get more accurate results

@@            Coverage Diff             @@
##           master   #19493      +/-   ##
==========================================
+ Coverage   66.58%   66.59%   +0.01%     
==========================================
  Files        1677     1678       +1     
  Lines       64238    64243       +5     
  Branches     6538     6539       +1     
==========================================
+ Hits        42773    42785      +12     
+ Misses      19766    19763       -3     
+ Partials     1699     1695       -4     

Flag	Coverage Δ
javascript	51.35% <85.00%> (+0.02%)	⬆️

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

Impacted Files	Coverage Δ
...allel-coordinates/src/ReactParallelCoordinates.jsx	0.00% <0.00%> (ø)
...ins/legacy-plugin-chart-sankey/src/ReactSankey.jsx	0.00% <0.00%> (ø)
superset-frontend/src/SqlLab/App.jsx	0.00% <ø> (ø)
...frontend/src/SqlLab/components/SouthPane/index.tsx	65.62% <ø> (ø)
...c/SqlLab/components/TemplateParamsEditor/index.tsx	75.00% <ø> (ø)
...set-frontend/src/components/ListViewCard/index.tsx	97.56% <ø> (ø)
superset-frontend/src/views/CRUD/utils.tsx	65.57% <ø> (ø)
...rontend/src/SqlLab/components/QueryTable/index.tsx	68.96% <50.00%> (+0.54%)	⬆️
...-ui-chart-controls/src/components/ColumnOption.tsx	85.71% <100.00%> (ø)
...-ui-chart-controls/src/components/MetricOption.tsx	94.73% <100.00%> (ø)
... and 10 more

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