Cleans up compose files

- Removes some whitespace
- Removes unnecessary environment variables

docker-compose-examples/grist-local-testing/docker-compose.yml

@@ -1,11 +1,8 @@
 services:
   grist:
     image: gristlabs/grist:latest
-    environment:
-      # Use Python 3 instead of 2.
-      PYTHON_VERSION: 3
     volumes:
       # Where to store persistent data, such as documents.
-      - ./grist_local_data:/persist
+      - ${GRIST_DATA_DIR:-./grist_local_data}:/persist
     ports:
       - 8484:8484

docker-compose-examples/grist-traefik-basic-auth/docker-compose.yml

@@ -1,5 +1,3 @@
-
-
 services:
   grist:
     image: gristlabs/grist:latest

docker-compose-examples/grist-with-postgres-redis-minio/docker-compose.yml

@@ -1,12 +1,7 @@
-
-
 services:
   grist:
     image: gristlabs/grist:latest
     environment:
-      # Use Python 3 instead of 2.
-      PYTHON_VERSION: 3
-
       # Postgres database setup
       TYPEORM_DATABASE: grist
       TYPEORM_USERNAME: grist