docs(bigquery): typo fix (#10209)

Author: Gurov Ilya

bigquery/google/cloud/bigquery/job.py

@@ -3073,7 +3073,7 @@ def done(self, retry=DEFAULT_RETRY, timeout=None):
  else:
  timeout = server_timeout_with_margin
 
- # Do not refresh is the state is already done, as the job will not
+ # Do not refresh if the state is already done, as the job will not
  # change once complete.
  if self.state != _DONE_STATE:
  self._query_results = self._client._get_query_results(