qubes-gui-runuser: fix parameters order for calloc

GCC 14 complains:

qubes-gui-runuser.c: In function ...pam_conv_callback...:
qubes-gui-runuser.c:48:23: error: ...calloc... sizes specified with ...sizeof... in the earlier argument and not in the later argument [-Werror=calloc-transposed-args]
   48 |         calloc(sizeof(struct pam_response), num_msg);
      |                       ^~~~~~
qubes-gui-runuser.c:48:23: note: earlier argument should specify number of elements, later size of each element
cc1: all warnings being treated as errors

QubesOS/qubes-issues#8915

gui-agent/qubes-gui-runuser.c

@@ -45,7 +45,7 @@ static int pam_conv_callback(int num_msg, const struct pam_message **msg,
 {
     int i;
     struct pam_response *resp_array =
-        calloc(sizeof(struct pam_response), num_msg);
+        calloc(num_msg, sizeof(struct pam_response));
 
     if (resp_array == NULL)
         return PAM_BUF_ERR;