style: remove unused variables (#2946)

Co-authored-by: realstealthninja <68815218+realstealthninja@users.noreply.github.com>

machine_learning/kohonen_som_trace.cpp

@@ -103,7 +103,7 @@ namespace machine_learning {
 void update_weights(const std::valarray<double> &x,
                     std::vector<std::valarray<double>> *W,
                     std::valarray<double> *D, double alpha, int R) {
-    int j = 0, k = 0;
+    int j = 0;
     int num_out = W->size();  // number of SOM output nodes
     // int num_features = x.size();  // number of data features
 

machine_learning/ordinary_least_squares_regressor.cpp

@@ -367,8 +367,6 @@ std::vector<float> predict_OLS_regressor(std::vector<std::vector<T>> const &X,
 
 /** Self test checks */
 void ols_test() {
-    int F = 3, N = 5;
-
     /* test function = x^2 -5 */
     std::cout << "Test 1 (quadratic function)....";
     // create training data set with features = x, x^2, x^3