test: Fix wrong comment

This commit fixes a wrong comment, claiming that the unit tests uses a
stack size of 16MB, where in fact it only uses 8MiB.

src/protocol.rs

@@ -1740,7 +1740,7 @@ mod test {
         // initialize secret and public key for the crypto server
         let (mut sk, mut pk) = (SSk::zero(), SPk::zero());
 
-        // Guranteed to have 16MB of stack size
+        // Guranteed to have 8MiB of stack size
         stacker::grow(8 * 1024 * 1024, || {
             StaticKEM::keygen(sk.secret_mut(), pk.secret_mut()).expect("unable to generate keys");
         });