remove unsused string

src/main/res/values/strings.xml

@@ -12,7 +12,6 @@
     <string name="actionbar_see_details">Details</string>
     <string name="actionbar_send_file">Send</string>
     <string name="actionbar_sort">Sort</string>
-    <string name="actionbar_sort_title">Sort by</string>
     <string name="sort_by">Sort by</string>
     <string name="menu_item_sort_by_name_a_z">A - Z</string>
     <string name="menu_item_sort_by_name_z_a">Z - A</string>