removed useless file on docker

docker.md

@@ -1,15 +0,0 @@
-# docker
-
-- [start docker service](#start-docker-service)
-
-
-## start docker service
-
-To start the docker service, use `systemctl`:
-```bash
-sudo systemctl start docker
-```
-If you want the docker service to be started at boot, use:
-```bash
-sudo systemctl enable --now docker
-```