Adjust the character picker layout a little so it will fit on the screen.

Previously when there were three rows of characters, the Cancel button
would hang off the edge a little.

Bug 1747709

core/res/res/layout/character_picker.xml

@@ -23,8 +23,8 @@
         android:id="@+id/characterPicker"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:padding="12dp"
-        android:verticalSpacing="8dp"
+        android:padding="4dp"
+        android:verticalSpacing="4dp"
         android:horizontalSpacing="8dp"
         android:stretchMode="spacingWidth"
         android:gravity="left"