fix(ingest): rectify filter for BigQuery external tables

In the SQL statement querying BigQuery table metadata, the `table_type`
is incorrectly filtered for external tables:

According to the [official
documentation](https://cloud.google.com/bigquery/docs/information-schema-tables#schema),
the `table_type` will be `EXTERNAL` for external tables. The query
incorrectly expected it to be `EXTERNAL TABLE` instead.

metadata-ingestion/src/datahub/ingestion/source/bigquery_v2/bigquery_schema.py

@@ -119,7 +119,7 @@ class BigqueryQuery:
         table_name) as p on
     t.table_name = p.table_name
 WHERE
-  table_type in ('BASE TABLE', 'EXTERNAL TABLE')
+  table_type in ('BASE TABLE', 'EXTERNAL')
 {table_filter}
 order by
   table_schema ASC,
@@ -146,7 +146,7 @@ class BigqueryQuery:
   and t.TABLE_NAME = tos.TABLE_NAME
   and tos.OPTION_NAME = "description"
 WHERE
-  table_type in ('BASE TABLE', 'EXTERNAL TABLE')
+  table_type in ('BASE TABLE', 'EXTERNAL')
 {table_filter}
 order by
   table_schema ASC,