Improve symbols test

Remove seed argument and check for disallowed undefined symbols

conflict_set_c_api_test.c

@@ -3,7 +3,7 @@
 #include <assert.h>
 
 int main(void) {
-  ConflictSet *cs = ConflictSet_create(0, 0);
+  ConflictSet *cs = ConflictSet_create(0);
   ConflictSet_WriteRange w;
   ConflictSet_Result result;
   ConflictSet_ReadRange r;