Dialer: track textColorPrimary back_arrow drawable from android attr

Change-Id: Ie4c2733280cefc21f519454dfa1b9f07212d96a0
diff --git a/java/com/android/dialer/widget/res/drawable/back_arrow.xml b/java/com/android/dialer/widget/res/drawable/back_arrow.xml
index 628543f..a3d1624 100644
--- a/java/com/android/dialer/widget/res/drawable/back_arrow.xml
+++ b/java/com/android/dialer/widget/res/drawable/back_arrow.xml
@@ -19,7 +19,7 @@
     android:viewportWidth="24.0"
     android:viewportHeight="24.0"
     android:autoMirrored="true"
-    android:tint="?attr/textColorPrimary">
+    android:tint="?android:attr/textColorPrimary">
   <path
       android:fillColor="@android:color/white"
       android:pathData="M20,11H7.83l5.59,-5.59L12,4l-8,8 8,8 1.41,-1.41L7.83,13H20v-2z"/>