Fix "unobstrusive" typo in appdata

data/gnome-sudoku.appdata.xml.in

@@ -6,7 +6,7 @@
   <_name>GNOME Sudoku</_name>
   <description>
     <_p>
-      GNOME Sudoku has a simple, unobstrusive interface with all the features
+      GNOME Sudoku has a simple, unobtrusive interface with all the features
       that make playing Sudoku fun. Games are automatically saved when you quit,
       and you can always come back to any game that you've played.
     </_p>