Fix spelling issue.

src/mlpack/methods/ann/ffn.hpp

@@ -273,7 +273,7 @@ class FFN
   //! Modify the initial point for the optimization.
   arma::mat& Parameters() { return parameter; }
 
-  //! Get the matrix of resposnses to the input data points.
+  //! Get the matrix of responses to the input data points.
   const arma::mat& Responses() const { return responses; }
   //! Modify the matrix of responses to the input data points.
   arma::mat& Responses() { return responses; }