Adjust OOjs UI TextInputWidget text style

White text shadow looked bad on Chrome/Linux where selected text
color is white.

Change-Id: I6723bc8ee0f6e2f77bb299216d56a844ac17a9f1
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/443
Merge "Adjust OOjs UI TextInputWidget text style"