fix: POSTGRES_PASSWORD key (#10573)

Fix POSTGRES_PASSWORD key, consistent with /docker/.env.example POSTGRES_PASSWORD

docker/volumes/db/roles.sql

@@ -1,5 +1,5 @@
 -- NOTE: change to your own passwords for production environments
-\set pgpass `echo "$PGPASSWORD"`
+\set pgpass `echo "$POSTGRES_PASSWORD"`
 
 ALTER USER authenticator WITH PASSWORD :'pgpass';
 ALTER USER pgbouncer WITH PASSWORD :'pgpass';