Remove some useless PG_ variables fron the s3-storage-provider env-file

These Postgres configuration variables are part of the `database.yaml` file
and don't need to be here.

roles/matrix-synapse/templates/synapse/ext/s3-storage-provider/env.j2

@@ -5,12 +5,6 @@ AWS_DEFAULT_REGION={{ matrix_synapse_ext_synapse_s3_storage_provider_config_regi
 ENDPOINT={{ matrix_synapse_ext_synapse_s3_storage_provider_config_endpoint_url }}
 BUCKET={{ matrix_synapse_ext_synapse_s3_storage_provider_config_bucket }}
 
-PG_USER={{ matrix_synapse_database_user }}
-PG_PASS={{ matrix_synapse_database_password }}
-PG_DB={{ matrix_synapse_database_database }}
-PG_HOST={{ matrix_synapse_database_host }}
-PG_PORT={{ matrix_synapse_database_port }}
-
 MEDIA_PATH=/matrix-media-store-parent/{{ matrix_synapse_media_store_directory_name }}
 
 UPDATE_DB_DURATION={{ matrix_synapse_ext_synapse_s3_storage_provider_update_db_day_count }}d