Remove dind tmpfs in test env

It wasn't changing anything in the test process, so this was a mistake to add.

Signed-off-by: Christina Ying Wang <christina@balena.io>

docker-compose.test.yml

@@ -60,9 +60,6 @@ services:
     environment:
       DOCKER_TLS_CERTDIR: ''
     command: --tls=false # --debug
-    tmpfs:
-    # Prevent dind creating a bunch of anonymous volumes on host
-      - /var/lib/docker
 
   sut:
     # Build the supervisor code for development and testing