fix: remove pgstac instructions

Author: gadomski

README.md

@@ -36,10 +36,6 @@ aws sso login --profile eoapi && eval "$(aws configure export-credentials --prof
 cdk diff # to show any differences
 ```
 
-### pgstac
-
-The **pgstac** database's connection parameters live in the `pgstac-db > db > Secret` resource in the `stac-fastapi-geoparquet-labs-375-infra` CloudFormation stack.
-
 ## Releasing and deploying
 
 Our deploys are triggered by Github releases (or by workflow dispatch, in a pinch).