docker-compose: break worker/web dependency

this results in constantly recreating/restarting the worker when it's
really not necessary for web config changes

Signed-off-by: Alex Suraci <asuraci@pivotal.io>

docker-compose.yml

@@ -37,7 +37,6 @@ services:
     image: concourse/concourse:local
     command: worker
     privileged: true
-    depends_on: [web]
     ports:
     - 7777:7777
     - 7788:7788