Update bigquery-configs.md (dbt-labs#4253)

Should specify taxonomy not organization.

## What are you changing in this pull request and why?
<!---
The `policy_tags` example delineates putting your organization ID in the
tag reference, but this should be the taxonomy ID. One line change.
-->

website/docs/reference/resource-configs/bigquery-configs.md

@@ -414,7 +414,7 @@ models:
   columns:
     - name: field
       policy_tags:
-        - 'projects/<gcp-project>/locations/<location>/taxonomies/<organization>/policyTags/<tag>'
+        - 'projects/<gcp-project>/locations/<location>/taxonomies/<taxonomy>/policyTags/<tag>'
 ```
 
 </File>