Remove version in test compose files

Signed-off-by: Guillaume Lours <guillaume.lours@docker.com>

ecs/testdata/input/simple-single-service.yaml

@@ -1,4 +1,3 @@
-version: "3"
 services:
   simple:
     image: nginx

ecs/testdata/invalid_network_mode.yaml

@@ -1,4 +1,3 @@
-version: "3"
 services:
   simple:
     image: nginx

tests/composefiles/aci-demo/aci_demo_multi_port.yaml

@@ -1,5 +1,3 @@
-version: '3.3'
-
 services:
   db:
     build: db

tests/composefiles/aci-demo/aci_demo_port.yaml

@@ -1,5 +1,3 @@
-version: '3.3'
-
 services:
   db:
     build: db

tests/composefiles/aci-demo/aci_demo_port_secrets.yaml

@@ -1,5 +1,3 @@
-version: '3.3'
-
 services:
   db:
     build: db

tests/composefiles/aci-demo/aci_demo_port_secrets_volumes.yaml

@@ -1,5 +1,3 @@
-version: '3.3'
-
 services:
   db:
     build: db

tests/composefiles/nginx.yaml

@@ -1,5 +1,3 @@
-version: "3.7"
-
 services:
   nginx:
     image: nginx