docker-compose, remove /etc/timezone because it's not available on some Linux systems

See discussion #4131

.devcontainer/docker-compose.yml

@@ -13,7 +13,6 @@ services:
       - 27017
     volumes:
       - /etc/localtime:/etc/localtime:ro
-      - /etc/timezone:/etc/timezone:ro
       - ./volumes/wekan-db:/data/db
       - ./volumes/wekan-db-dump:/dump
 
@@ -38,7 +37,6 @@ services:
       - wekandb-dev
     volumes:
       - /etc/localtime:/etc/localtime:ro
-      - /etc/timezone:/etc/timezone:ro
       - ../client:/home/wekan/app/client
       - ../models:/home/wekan/app/models
       - ../config:/home/wekan/app/config

docker-compose.yml

@@ -663,7 +663,6 @@ services:
       - wekandb
     volumes:
       - /etc/localtime:/etc/localtime:ro
-      - /etc/timezone:/etc/timezone:ro
 
 #---------------------------------------------------------------------------------
 # ==== OPTIONAL: SHARE DATABASE TO OFFICE LAN AND REMOTE VPN ====

torodb-postgresql/docker-compose.yml

@@ -110,7 +110,6 @@ services:
       - DEBUG
     volumes:
       - /etc/localtime:/etc/localtime:ro
-      - /etc/timezone:/etc/timezone:ro
   postgres:
     image: quay.io/wekan/postgres:9.6
     networks:
@@ -121,7 +120,6 @@ services:
       - "5432:5432"
     volumes:
       - /etc/localtime:/etc/localtime:ro
-      - /etc/timezone:/etc/timezone:ro
   mongodb:
     image: mongo:3.2
     networks:
@@ -144,7 +142,6 @@ services:
         mongod --replSet rs1
     volumes:
       - /etc/localtime:/etc/localtime:ro
-      - /etc/timezone:/etc/timezone:ro
   wekan:
     image: quay.io/wekan/wekan
     container_name: wekan-app
@@ -615,7 +612,6 @@ services:
       - mongodb
     volumes:
       - /etc/localtime:/etc/localtime:ro
-      - /etc/timezone:/etc/timezone:ro
 
 #---------------------------------------------------------------------------------
 # ==== OPTIONAL: SHARE DATABASE TO OFFICE LAN AND REMOTE VPN ====