Don't override the text color for bordless buttons.

The default borderless button style uses the colorPrimary attribute to
style it. This is already the color that is needed.

Test: Build setupwizard and run through in day and night mode. Verify
that "skip" and "refresh" buttons are now visible in day mode, and are
blue.
Fixes: 70865381

Change-Id: I26d92594689098fe915f1dac73685dbe4dbfdb59