sasl-mechlist.c: Cast function pointer to the expected type

This fixes a build failure with GCC 14,

Related to:

  <https://fedoraproject.org/wiki/Changes/PortingToModernC>
  <https://fedoraproject.org/wiki/Toolchain/PortingToModernC>

sasl-mechlist.c

@@ -34,7 +34,7 @@ main(int argc, char **argv)
 	int ret, i;
 	const char *mechs, **globals;
 	sasl_callback_t callbacks[] = {
-		{SASL_CB_GETOPT, my_getopt, NULL},
+		{SASL_CB_GETOPT, (int (*)(void)) my_getopt, NULL},
 		{SASL_CB_LIST_END},
 	};
 	sasl_conn_t *connection;