Docs: fix punctuation on Color modes page (it's -> its)

[mrlife]

Description

Remove apostrophe from "it's"

Motivation & Context

Fix grammar

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

[julien-deramond]

Thanks!