test(runtime-c-api) Free allocations.

Don't forget to free `context_data` :-).

lib/runtime-c-api/tests/test-import-function.c

@@ -100,5 +100,6 @@ int main()
     wasmer_import_func_destroy(func);
     printf("Destroy instance\n");
     wasmer_instance_destroy(instance);
+    free(context_data);
     return 0;
 }