Fix Docker release process for dbt-postgres (#9828)

* revert to the 1.7 approach, 1.8 will be handled in the new repo

.changes/unreleased/Fixes-20240327-150013.yaml

@@ -0,0 +1,7 @@
+kind: Fixes
+body: '"Fix Docker release process to account for both historical and current versions
+  of `dbt-postgres`'
+time: 2024-03-27T15:00:13.388268-04:00
+custom:
+  Author: mikealfare
+  Issue: "9827"

docker/Dockerfile

@@ -62,7 +62,7 @@ RUN python -m pip install --no-cache-dir "git+https://github.com/dbt-labs/${dbt_
 # dbt-postgres
 ##
 FROM base as dbt-postgres
-RUN python -m pip install --no-cache-dir "git+https://github.com/dbt-labs/${dbt_postgres_ref}#egg=dbt-postgres"
+RUN python -m pip install --no-cache-dir "git+https://github.com/dbt-labs/${dbt_postgres_ref}#egg=dbt-postgres&subdirectory=plugins/postgres"
 
 
 ##
@@ -130,4 +130,4 @@ RUN apt-get update \
   RUN python -m pip install --no-cache "git+https://github.com/dbt-labs/${dbt_bigquery_ref}#egg=dbt-bigquery"
   RUN python -m pip install --no-cache "git+https://github.com/dbt-labs/${dbt_snowflake_ref}#egg=dbt-snowflake"
   RUN python -m pip install --no-cache "git+https://github.com/dbt-labs/${dbt_spark_ref}#egg=dbt-spark[${dbt_spark_version}]"
-  RUN python -m pip install --no-cache "git+https://github.com/dbt-labs/${dbt_postgres_ref}#egg=dbt-postgres"
+  RUN python -m pip install --no-cache "git+https://github.com/dbt-labs/${dbt_postgres_ref}#egg=dbt-postgres&subdirectory=plugins/postgres"