Explicitly set textColor value for Widget.Car.CheckBox style.

Bug: 135489709
Test: Verify on SupportCarDemo's buttons

Change-Id: Ifcd7a1f840736a033e9380dc23fa17de17b9308c

diff --git a/car/core/res/values/styles.xml b/car/core/res/values/styles.xml
index a0535a3..911fdcb 100644
--- a/car/core/res/values/styles.xml
+++ b/car/core/res/values/styles.xml

@@ -543,13 +543,14 @@
     <eat-comment />
 
     <style name="Widget.Car.CheckBox" parent="Widget.AppCompat.CompoundButton.CheckBox">
+        <item name="android:textColor">@color/car_primary_text</item>
         <item name="android:textAppearance">@style/TextAppearance.Car.Body1</item>
         <item name="android:buttonTint">?android:attr/colorAccent</item>
         <item name="buttonTint">?android:attr/colorAccent</item>
     </style>
 
     <style name="Widget.Car.CheckBox.Light">
-        <item name="android:textAppearance">@style/TextAppearance.Car.Body1.Light</item>
+        <item name="android:textColor">@color/car_primary_text_light</item>
     </style>
 
     <!-- ================== -->