feat(Docker Compose): Remove obsolete version variable

see: https://github.com/docker/compose/issues/11628

uptimekuma/docker-compose.local.yml

@@ -1,7 +1,5 @@
 ---
 
-version: "3.8"
-
 services:
   uptimekuma:
     ports:

uptimekuma/docker-compose.traefik.yml

@@ -1,7 +1,5 @@
 ---
 
-version: "3.8"
-
 networks:
   default:
     name: ${TRAEFIK_NETWORK_NAME:-traefik}

uptimekuma/docker-compose.yml

@@ -1,7 +1,5 @@
 ---
 
-version: "3.8"
-
 volumes:
   uptimekuma:
     name: ${UPTIMEKUMA_VOLUME_NAME:-uptimekuma}