Controlled vocabulary data paths for CORDEX data

According to Jason Evans the DRS path for CORDEX CMIP6 data should be `CORDEX/CMIP6` and `output` should be `rcm` e.g., `test-data/CORDEX/CMIP6/rcm/...` currently it is `test-data/CORDEX-CMIP6/output/...` in [data_standards.md](https://github.com/AusClimateService/data-code-group/blob/main/data_standards.md).