[mercure] v0.8 compatibility

Author: dunglas

symfony/mercure-bundle/0.1/manifest.json

@@ -7,7 +7,7 @@
     },
     "env": {
         "#1": "See https://symfony.com/doc/current/mercure.html#configuration",
-        "MERCURE_PUBLISH_URL": "http://mercure/hub",
+        "MERCURE_PUBLISH_URL": "http://mercure/.well-known/mercure",
         "#2": "The default token is signed with the secret key: !ChangeMe!",
         "MERCURE_JWT_TOKEN": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJtZXJjdXJlIjp7InB1Ymxpc2giOltdfX0.Oo0yg7y4yMa1vr_bziltxuTCqb8JVHKxp-f_FwwOim0"
     },