Remove version from docker-compose.yml files #845

See https://github.com/compose-spec/compose-spec/blob/master/spec.md#version-and-name-top-level-elements

docker/docker-compose.development.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   db:
     image: postgres:13

docker/docker-compose.production.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   www:
     # Update this to the latest stable version before deploying.

docker/docker-compose.testing.common.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   www:
     image: farmos/farmos:3.x-dev

docker/docker-compose.testing.mariadb.yml

@@ -1,5 +1,4 @@
 # Inherits from docker-compose.testing.common.yml
-version: '3'
 services:
   db:
     image: mariadb:10

docker/docker-compose.testing.pgsql.yml

@@ -1,5 +1,4 @@
 # Inherits from docker-compose.testing.common.yml
-version: '3'
 services:
   db:
     image: postgres:13

docker/docker-compose.testing.sqlite.yml

@@ -1,3 +1,2 @@
 # Inherits from docker-compose.testing.common.yml
-version: '3'
 services: {  }