cleanup bug in run_rc_validation.sh

Saw this in the console:
```

-----------------Cleaning up BigQuery & Pubsub-----------------
/usr/lib/google-cloud-sdk/platform/bq/bq.py:45:
DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation
for alternative uses
import imp
FATAL Flags parsing error: Unknown command line flag 'rf'
Run 'bq.py
help' to get help
Deleted topic [projects/XXX/topics/leader_board-ehudm-java-topic-0115_19681].

```

Imported from Jira [BEAM-9131](https://issues.apache.org/jira/browse/BEAM-9131). Original Jira may contain additional context.
Reported by: udim.