Update Dashboard padding

- make it the same as the one used for PreferenceFragments

Change-Id: I9575f0fef4492d76afb25b10af201839709517e9
diff --git a/res/layout/dashboard.xml b/res/layout/dashboard.xml
index e63acd7..c6c7292 100644
--- a/res/layout/dashboard.xml
+++ b/res/layout/dashboard.xml
@@ -18,8 +18,8 @@
     android:id="@+id/dashboard"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:paddingStart="12dp"
-    android:paddingEnd="12dp"
+    android:paddingStart="@*android:dimen/preference_fragment_padding_side"
+    android:paddingEnd="@*android:dimen/preference_fragment_padding_side"
     android:scrollbarStyle="outsideOverlay"
     android:background="@color/dashboard_background_color">