Set drop target font weight to medium.

Bug: 235886741
Test: manual.
Change-Id: Ie5b3f4159dee7e2eb8e614a15b57a0929f8eae71
diff --git a/res/values/styles.xml b/res/values/styles.xml
index 65bba7b..a8cbf08 100644
--- a/res/values/styles.xml
+++ b/res/values/styles.xml
@@ -274,7 +274,7 @@
     </style>
 
     <!-- Drop targets -->
-    <style name="DropTargetButtonBase" parent="@android:style/TextAppearance.DeviceDefault">
+    <style name="DropTargetButtonBase" parent="@android:style/TextAppearance.DeviceDefault.Medium">
         <item name="android:drawablePadding">@dimen/drop_target_button_drawable_padding</item>
         <item name="android:padding">14dp</item>
         <item name="android:textColor">@color/drop_target_text</item>