refactor: Remove unnecessary variable

nextcloud/.env

@@ -16,7 +16,6 @@ NEXTCLOUD_ADMIN_PASSWORD: password
 # DATABASE
 # Voir la description ../postgres/README.md
 
-POSTGRES_IMAGE=postgres:12.7-alpine
 POSTGRES_USER=user-example
 POSTGRES_PASSWORD=password-example
 POSTGRES_DB=postgres-database-name-example

nextcloud/docker-compose.yml

@@ -59,7 +59,7 @@ services:
 
   nextcloud-postgres:
     container_name: ${POSTGRES_CONTAINER_NAME}
-    image: ${POSTGRES_IMAGE}
+    image: ${POSTGRES_IMAGE:-postgres:12.7-alpine}
     restart: always
     environment:
       POSTGRES_USER: ${POSTGRES_USER}