Fix the text contrast for biometric header

Since the color of text was using material dark color from material
theme, which is different from the one in Settings. Removing the text
color specified in the style can fix this problem.

Fix: 182437787
Fix: 187145158
Test: visual verified
Change-Id: I4ad5004a6811713982d0d22a8050889d75cc3a5f
diff --git a/res/values/styles.xml b/res/values/styles.xml
index e8670f9..c72b3a5 100644
--- a/res/values/styles.xml
+++ b/res/values/styles.xml
@@ -392,7 +392,6 @@
 
     <style name="BiometricHeaderStyle" parent="@*android:style/TextAppearance.DeviceDefault.Subhead">
         <item name="android:paddingTop">16dp</item>
-        <item name="android:textColor">@color/primary_dark_material_light</item>
         <item name="android:lineSpacingMultiplier">1.2</item>
     </style>