day 4 buzzer pin correction

docs/solutions/04/04.md

@@ -12,7 +12,7 @@ Here is my solution, using the LED and the buzzer. Try to do it yourself first,
 
 ```c++
 const int led = 48;
-const int buzzer = 14;
+const int buzzer = 46;
 const int freq = 800;
 
 const int wait = 200;  // Duration of a unit