ex07 test fix

[MykytaOksak]

Running make test gives you an error:

src/test.c:10:12: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘void *’ [-Werror=format=]
   10 | printf("%s\n", data);
      | ~^ ~~~~
      | | |
      | | void *
      | char *
      | %p

Changing the formatting specifier for void * to %p fixes this up.