Cube pre aggregations with export bucket strategy still create tables in the data warehouse

**Describe the bug**
We are using the pre aggregations with Cube leveraging AWS Redshift as the data warehouse. We tried the export bucket strategy to implement the pre aggregations, and it should export the data from Redshift to S3, then move the data from S3 to Cube Store.
The issue is that it still uses a pre-aggregation schema to first create the tables on Redshift, then it UNLOADS the data from Redshift to S3, and then from S3 to Cube Store.

**To Reproduce**
Steps to reproduce the behavior:
1. Configure Cube to use the export bucket strategy
2. Configure a pre-aggregation in one Cube
3. See that data are created both in the data warehouse and also in S3

**Expected behavior**
The expected behavior is to have the data only created on S3 and not in a new pre aggregations schema inside the data warehouse.

**Version:**
0.30.9