fix(slider): corrects contrast bug caused by template default arg

[cdransf]

Description

Corrects the contrast issue observed between the fill element and slider track that caused the fill element to be difficult to see.

• Adjusts colors per design feedback.
• Removes default control/template value that caused contrast issue in dark modew.

Validation steps

1. Open Storybook URL
2. Navigate to slider
3. Change theme from light to dark
4. Enable testing preview
5. Scroll to filled offset and verify offset and track have sufficient contrast

Screenshots

To-do list

• I have read the contribution guidelines.
• I have updated relevant storybook stories and templates.
• I have tested these changes in Windows High Contrast mode.
• If my change impacts other components, I have tested to make sure they don't break.
• If my change impacts documentation, I have updated the documentation accordingly.
• ✨ This pull request is ready to merge. ✨

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Latest commit: ca1eb32

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[github-actions]

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Summary

Total size: 2.25 MB^*

🎉 No changes detected in any packages

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[github-actions]

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[marissahuysentruyt]

Thanks for digging into the gray values- glad we got them corrected!

Looking at prod, is this PR supposed to address main? I think I see the same issue, so if we fix it on main, could we just cherry pick over to spectrum-two?

[cdransf]

Thanks for digging into the gray values- glad we got them corrected!

Looking at prod, is this PR supposed to address main? I think I see the same issue, so if we fix it on main, could we just cherry pick over to spectrum-two?

Absolutely! I lifted everything over to main and squashed it down so we can cherry-pick in a follow up PR. ✨