columnar_first_row test fails when run in parallel with columnar_query test

When running columnar_first_row and columnar_query in parallel sometimes columnar_first_row fails with the following error:
```diff
SELECT row_count, first_row_number FROM columnar.stripe a
WHERE a.storage_id = columnar.get_storage_id('col_table_1'::regclass)
ORDER BY stripe_num;
- row_count | first_row_number
----------------------------------------------------------------------
- 10 | 1
- 12 | 300001
- 1000 | 450001
- 1000 | 451001
- 350 | 452001
-(5 rows)
-
+ERROR: could not open relation with OID 17223
VACUUM FULL col_table_1;
```

Example of failed test: https://app.circleci.com/pipelines/github/citusdata/citus/26106/workflows/75d00ea9-23f8-4bff-a927-bced19e1f81b/jobs/736713

For reference @jeff-davis had these thoughts on this issue in #6184:
> It seems that col_table_1 is only referenced in columnar_first_row_number.sql so I still don't understand the diagnosis. How does columnar_query.sql conflict with it?