Update ColorConversionExtensions.shared.cs

[stephenquan]

Description of Change

This PR fixes a culture-specific formatting issue in the ToCmykaString() method to ensure consistent behavior across different culture settings.

• Updated ToCmykaString() to explicitly use the provided CultureInfo parameter for all numeric formatting operations
• Replaced interpolated string format specifiers (:P0) with explicit ToString("P0", cultureInfo) calls

Linked Issues

• Fixes Issue [BUG] Color conversion not behaving as expected #2873

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (existing test passes with this change)
• Has samples (no change in samples needed since there was no API change)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: (no change needed since there was no API change)

Additional information

I forced the CurrentInfo.CurrentCulture to "de-DE" to repro the failing xUnit test problem and applied fixes until the xUnit tests started passing.

[Copilot]

Pull Request Overview

This PR fixes a culture-specific formatting issue in the ToCmykaString() method to ensure consistent behavior across different culture settings.

• Updated ToCmykaString() to explicitly use the provided CultureInfo parameter for all numeric formatting operations
• Replaced interpolated string format specifiers (:P0) with explicit ToString("P0", cultureInfo) calls