fix: Fix dashboards in end-to-end-security demo (#287)

Author: sbernauer

demos/end-to-end-security/README.md

@@ -7,13 +7,13 @@
 5. `pgdump` the Postgres and update the dump in Git. For that shell into `postgresql-superset-0` and execute
 
 ```sh
-export PGPASSWORD="$POSTGRES_POSTGRES_PASSWORD"
+export PGPASSWORD=$(cat "${POSTGRES_POSTGRES_PASSWORD_FILE}")
 
-pg_dumpall -Upostgres | gzip -c > /tmp/dump.sql.gz
+pg_dumpall -Upostgres > /tmp/dump.sql
 ```
 
 Afterwards copy the dump to your local machine using
 
 ```sh
-kubectl cp postgresql-superset-0:/tmp/dump.sql.gz postgres_superset_dump.sql.gz
+kubectl cp postgresql-superset-0:/tmp/dump.sql postgres_superset_dump.sql
 ```