fix collapse/expand icon color

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/src/main/res/drawable/baseline_unfold_less_24.xml

@@ -1,9 +1,8 @@
 <vector
     android:height="24dp"
-    android:tint="?attr/colorControlNormal"
     android:viewportHeight="24"
     android:viewportWidth="24"
     android:width="24dp"
     xmlns:android="http://schemas.android.com/apk/res/android">
-    <path android:fillColor="@android:color/white" android:pathData="M7.41,18.59L8.83,20 12,16.83 15.17,20l1.41,-1.41L12,14l-4.59,4.59zM16.59,5.41L15.17,4 12,7.17 8.83,4 7.41,5.41 12,10l4.59,-4.59z"/>
+    <path android:fillColor="@color/grey_600" android:pathData="M7.41,18.59L8.83,20 12,16.83 15.17,20l1.41,-1.41L12,14l-4.59,4.59zM16.59,5.41L15.17,4 12,7.17 8.83,4 7.41,5.41 12,10l4.59,-4.59z"/>
 </vector>

app/src/main/res/drawable/baseline_unfold_more_24.xml

@@ -1,9 +1,8 @@
 <vector
     android:height="24dp"
-    android:tint="?attr/colorControlNormal"
     android:viewportHeight="24"
     android:viewportWidth="24"
     android:width="24dp"
     xmlns:android="http://schemas.android.com/apk/res/android">
-    <path android:fillColor="@android:color/white" android:pathData="M12,5.83L15.17,9l1.41,-1.41L12,3 7.41,7.59 8.83,9 12,5.83zM12,18.17L8.83,15l-1.41,1.41L12,21l4.59,-4.59L15.17,15 12,18.17z"/>
+    <path android:fillColor="@color/grey_600" android:pathData="M12,5.83L15.17,9l1.41,-1.41L12,3 7.41,7.59 8.83,9 12,5.83zM12,18.17L8.83,15l-1.41,1.41L12,21l4.59,-4.59L15.17,15 12,18.17z"/>
 </vector>