web,jvb: remove ENABLE_MULTISTREAM

It's not enabled by default and there is no way to disable it any
longer.

We keep setting the flags in config.js though, this is so old mobile
versions without the new default behavior can enable it.

docker-compose.yml

@@ -88,7 +88,6 @@ services:
             - ENABLE_TRANSCRIPTIONS
             - ENABLE_XMPP_WEBSOCKET
             - ENABLE_JAAS_COMPONENTS
-            - ENABLE_MULTI_STREAM
             - ETHERPAD_PUBLIC_URL
             - ETHERPAD_URL_BASE
             - E2EPING_NUM_REQUESTS
@@ -313,7 +312,6 @@ services:
             - DOCKER_HOST_ADDRESS
             - ENABLE_COLIBRI_WEBSOCKET
             - ENABLE_OCTO
-            - ENABLE_MULTI_STREAM
             - JVB_ADVERTISE_IPS
             - JVB_ADVERTISE_PRIVATE_CANDIDATES
             - JVB_AUTH_USER