WebUI Dark Mode: fix some accidentally black text

R=hcarmona@chromium.org
BUG=883049

Change-Id: I0f2b4f97c130bbca75780bbcfccdd902f85956e4
Reviewed-on: https://chromium-review.googlesource.com/c/1455738
Auto-Submit: Dan Beam <dbeam@chromium.org>
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629684}
1 file changed