Change Alloy repo (#4297)

## What are you changing in this pull request and why?

Replacing the (defunct) postgres repo listed on the Alloy DB page to
match the postgres setup instructions

## Checklist

- [x] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
and [About
versioning](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
so my content adheres to these guidelines.
- [x] Add a checklist item for anything that needs to happen before this
PR is merged, such as "needs technical review" or "change base branch."

website/docs/docs/core/connect-data-platform/alloydb-setup.md

@@ -3,7 +3,7 @@ title: "AlloyDB setup"
 meta:
   maintained_by: Community?
   authors: 'dbt-labs'
-  github_repo: 'dbt-labs/dbt-postgres'
+  github_repo: 'dbt-labs/dbt-core'
   pypi_package: 'dbt-postgres'
   min_core_version: 'v1.0.0'
   cloud_support: Not Supported