Remove not used using declaration

This CL removes a not used using declaration
which will cause a warning when compiled with
-Wunused-local-typedef under gcc.

Change-Id: Ie4cfd5d1fed9bee860e387545e60d92d257da4f4

include/ceres/numeric_diff_cost_function.h

diff --git a/include/ceres/numeric_diff_cost_function.h b/include/ceres/numeric_diff_cost_function.h
index 493412b..c69f262 100644
--- a/include/ceres/numeric_diff_cost_function.h
+++ b/include/ceres/numeric_diff_cost_function.h
@@ -206,7 +206,6 @@
 
     using ParameterDims =
         typename SizedCostFunction<kNumResiduals, Ns...>::ParameterDims;
-    using Parameters = typename ParameterDims::Parameters;
 
     constexpr int kNumParameters = ParameterDims::kNumParameters;
     constexpr int kNumParameterBlocks = ParameterDims::kNumParameterBlocks;