Fix the following warnings (with ENABLE_READ_VIEW defined):

```
./perf/lua/column_scan_module.c:59:18: error: unused variable ‘index_id’ [-Werror=unused-variable]
   59 |         uint32_t index_id = luaL_checkinteger(L, 2);
      |                  ^~~~~~~~

./perf/lua/column_scan_module.c:149:18: error: unused variable ‘index_id’ [-Werror=unused-variable]
  149 |         uint32_t index_id = luaL_checkinteger(L, 2);
      |                  ^~~~~~~~
```

NO_DOC=perf test
NO_TEST=perf test
NO_CHANGELOG=perf test