fix: warning text color is not obvious in dark mode

[a110605]

Summary

Fixes #15169

Occurred changes and/or fixed issues

In harvester, the warning button text doens't look obviously in dark mode. Light mode looks fine.

Technical notes summary

Areas or cases that should be tested

Areas which could experience regressions

Screenshot/Video

Before

After

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes
• The PR has been reviewed in terms of Accessibility

[nwmac]

@a110605 This will need a rebase to pick up a test fix in the master branch