refactoring: realigned code, removed unused include and corrected description

src/convert_M_in_KM.c

@@ -1,7 +1,6 @@
-
 #include "convert_M_in_KM.h"
-#include <stdio.h>
-//convert length for double m into km
+
+// convert length for double metre into kilometre
 double meter_to_kilometer(double meter) {
     return meter / 1000.0;
 }