Remove hardcode for textcolor in spinner item.

Remove the "android:textcolor" because "Android:textAppearance"
will set the textcolor to "?attr/textColorPrimary".
Set adapter has same theme as spinner, so view inside adapter
can be inflatered correctly.

Bug: 32592245
Test: screenshot
Change-Id: If7a78ede0a029aa9fcd8f9b324a423d477c65ad7