User adding screen: Improve version number text

Make it white. See bug for the screenshot

Bug: 1018143
Change-Id: I697af356b786f824ac53907e63b5cdcb92d37faf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1899382Reviewed-by: Denis Kuznetsov [CET] <antrim@chromium.org>
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714210}

ui/login/oobe.css

@@ -200,6 +200,10 @@ span.bold {
   z-index: 1;
 }
 
+html[screen=user-adding] #version-labels {
+  color: white;
+}
+
 #bluetooth-name {
   background: rgba(255,255,255,.17);
   border-radius: 4px;