[#437] Fix color of default loading button in high contrast light mode

[pylapp]

Related issues

#437

Description

In default loading button change color if high contrast light mode

Motivation & Context

Types of change

• Bug fix (non-breaking which fixes an issue)

Previews

Checklist

Contribution

• I have read the contributing guidelines

Accessibility

• My change follows accessibility good practices

Design

• My change respects the design guidelines of Orange Unified Design System

Development

• My change follows the developer guide
• I checked my changes do not add new SwiftLint warnings
• I have added unit tests to cover my changes (optional)

Documentation

• My change introduces changes to the documentation and/or I have updated the documentation accordingly

Checklist (for Core Team only)

• The evolution have been tested and the project builds for iPhones and iPads
• Code review has been done by reviewers according to CODEOWNERS file
• (NA) Design review has been done
• (NA) Accessibility review has been done
• (NA) Q/A team has tested the evolution
• Documentation has been updated if relevant
• Internal files have been updated if relevant (like CONTRIBUTING, DEVELOP, THIRD_PARTY, CONTRIBUTORS, NOTICE)
• CHANGELOG has been updated respecting keep a changelog rules and reference the issues
• The wiki has been updated if needed (optional)

[pylapp]

@ludovic35 The PR on the demo app should be reviewed and merged before: Orange-OpenSource/ouds-ios-design-system-toolbox#18

Commit message:

fix: default loading button on high contrast light mode (#437) (#708)