Remove includes in _impl header if main header contains include

Note that we consider the wider include to `core` as being sufficient.

src/mlpack/methods/ann/ffn_impl.hpp

@@ -15,8 +15,6 @@
 // In case it hasn't been included yet.
 #include "ffn.hpp"
 
-#include <mlpack/core/util/log.hpp>
-
 namespace mlpack {
 
 template<typename OutputLayerType,

src/mlpack/methods/det/dt_utils_impl.hpp

@@ -15,7 +15,6 @@
 
 #include "dt_utils.hpp"
 #include <mlpack/core/tree/enumerate_tree.hpp>
-#include <mlpack/core/util/log.hpp>
 
 namespace mlpack {
 

src/mlpack/methods/det/dtree_impl.hpp

@@ -15,8 +15,6 @@
 #include <stack>
 #include <vector>
 
-#include <mlpack/core/util/log.hpp>
-
 namespace mlpack {
 
 /**

src/mlpack/methods/emst/dtb_impl.hpp

@@ -14,8 +14,6 @@
 
 #include "dtb_rules.hpp"
 
-#include <mlpack/core/util/log.hpp>
-
 namespace mlpack {
 
 /**

src/mlpack/methods/kmeans/kmeans_impl.hpp

@@ -13,7 +13,6 @@
 #include "kmeans.hpp"
 
 #include <mlpack/core/distances/lmetric.hpp>
-#include <mlpack/core/util/log.hpp>
 #include <mlpack/core/util/sfinae_utility.hpp>
 #include <mlpack/core/util/size_checks.hpp>