Fix typo

* NEWS, spot/graph/graph.hh: here.

NEWS

@@ -141,7 +141,7 @@ New in spot 2.9.1 (2020-07-15)
 
   - simplify_acceptance() missed some patterns it should have been
     able to simplify.  For instance Fin(0)&(Fin(1)|Fin(2)|Fin(4))
-    should simplify to Fin(1)|Fin(2)|Fin(4) adter adding {1,2,4} to
+    should simplify to Fin(1)|Fin(2)|Fin(4) after adding {1,2,4} to
     every place where 0 occur, and then the acceptance would be
     renumbered to Fin(0)|Fin(1)|Fin(2).  This is now fixed.
 

spot/graph/graph.hh

@@ -861,7 +861,7 @@ namespace spot
       return &ss - &states_.front();
     }
 
-    /// Conveart a storage reference into an edge number
+    /// Convert a storage reference into an edge number
     edge index_of_edge(const edge_storage_t& tt) const
     {
       SPOT_ASSERT(!edges_.empty());