Revert "Fix environment timezone"

This reverts commit cba045df69.

docker-compose.nginx.yml

@@ -27,7 +27,7 @@ services:
       # - ${GITLAB_PKI_CHAIN_PATH}:/etc/ssl/certs/pki_chain.pem:ro
     environment:
       # timezone inside container
-      - TZ: ${TZ}
+      - TZ
     ports:
       - ${HTTPS_PORT}:443
       - ${HTTP_PORT}:80

docker-compose.yml

@@ -18,7 +18,7 @@ services:
       - ${POSTGRES_DATA_PATH}:/var/lib/postgresql/data
     environment:
       # timezone inside container
-      - TZ: ${TZ}
+      - TZ
 
       # necessay Postgres options/variables
       - POSTGRES_USER
@@ -45,7 +45,7 @@ services:
       - ${MATTERMOST_CLIENT_PLUGINS_PATH}:/mattermost/client/plugins:rw
     environment:
       # timezone inside container
-      - TZ: ${TZ}
+      - TZ
 
       # necessary Mattermost options/variables (see env.example)
       - MM_SQLSETTINGS_DRIVERNAME