Update example: Use proper library

en/firmware/epicardium_api_development.md

@@ -38,7 +38,7 @@ The `*.c`-files need to be added to [`epicardium/modules/meson.build`](https://g
 
 An exemplary implementation to the declaration above could look like the following:
 ```c
-#include "example.h"
+#include <stdio.h>
 
 void epic_example_call(int example_param_a, uint8_t example_param_b)
 {