Make census builder run without errors on spatial datasets

Author: prathapsridharan

tools/cellxgene_census_builder/SPATIAL-README.md

@@ -1,8 +1,9 @@
 ## Development Environment Setup and Run
 
-- Install `cellxgene_census` package [from source](../../api/python/cellxgene_census/README.md)
 - `pip install -e tools/cellxgene_census_builder`
 
   **NOTE:** When running the builder on MacOS, unpin `pyarrow` in [census builder pyproject.toml](./pyproject.toml)
 
+- `pip install -e api/python/cellxgene_census`
+
 - [Dev tools for spatial](./spatial_dev_tools/) contains scripts and notebooks to aid development and testing