Use more standard Unicode notations in keyboard layout resource files.

bug: 5988656
Change-Id: Ie2416ccd790f29934a37e9dc77d7525e5113048a
diff --git a/java/res/drawable/btn_center.xml b/java/res/drawable/btn_center.xml
index 9998b56..3ac2129 100644
--- a/java/res/drawable/btn_center.xml
+++ b/java/res/drawable/btn_center.xml
@@ -37,4 +37,4 @@
         android:drawable="@drawable/btn_center_default" />
     <item
         android:drawable="@drawable/btn_center_default" />
-</selector>
\ No newline at end of file
+</selector>