Increase text contrast

[ithinkihaveacat]

WHAT

Increase the contrast of the "sign-in" button.

WHY

Before:

After:

HOW

Explicitly specify secondaryChipColors(). Might also be a good idea to convert the Chip() to ActionSetting() for consistency too but going with the less invasive change.

Checklist 📋

• Add explicit visibility modifier and explicit return types for public declarations
• Run spotless check
• Run tests
• Update metalava's signature text files

[yschimke]

Run './gradlew :media:sample:spotlessApply' to fix these violations.