Fix wat and exports memory leak in all examples

lib/c-api/examples/instance.c

@@ -77,6 +77,7 @@ int main(int argc, const char* argv[]) {
 
     printf("Results of `add_one`: %d\n", results_val[0].of.i32);
 
+    wasm_extern_vec_delete(&exports);
     wasm_store_delete(store);
     wasm_engine_delete(engine);
 }