Update README

You should update the README instructions [here](https://github.com/edanalytics/dbt_synth_data/blob/v0.1.0/README.md?plain=1#L57) to be add `"dbt_packages/dbt_synth_data/macros"` instead as the package name has been changed in this [commit](https://github.com/edanalytics/dbt_synth_data/commit/91c4aad69a5573628b60702bdc36b809be58579e)