[ci skip] Fix obsolete version attribute in docker-compose.yml (#2207)

Author: ybiquitous

docker-compose.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   nukkit:
     build: ./
@@ -12,4 +11,4 @@ services:
 volumes:
   data:
     external: true
-    name: nukkit-data
+    name: nukkit-data