chore: use iwyu on numerical_methods/**.cpp

numerical_methods/gram_schmidt.cpp

@@ -28,12 +28,10 @@
  * @author [Akanksha Gupta](https://github.com/Akanksha-Gupta920)
  */
 
-#include <array>     /// for std::array
-#include <cassert>   /// for assert
-#include <cmath>     /// for fabs
-#include <iostream>  /// for io operations
-
-#include "math.h"
+#include <array>     // for array
+#include <cassert>   // for assert
+#include <cmath>     // for fabs, NAN
+#include <iostream>  // for operator<<, basic_ostream, char_traits, cout
 
 /**
  * @namespace numerical_methods