fix(tests): correct C test signed compare
```
/runner/_work/enarx/enarx/tests/c-tests/sgx_get_att_quote.c: In function 'main':
/runner/_work/enarx/enarx/tests/c-tests/sgx_get_att_quote.c:33:14: warning: comparison of integer expressions of different signedness: 'ssize_t' {aka 'long int'} and 'long unsigned int' [-Wsign-compare]
33 |     if (size > sizeof(buf))
|
```
@@ -30,7 +30,7 @@ int main(void) {
return 0;
/* Ooops, the test fails because of false assumptions */
- if (size > sizeof(buf))
+ if (size > (ssize_t) sizeof(buf))
return 1000;
ssize_t quote_size = get_att(nonce, sizeof(nonce), buf, size, &technology);
