Update .env, remove SESSION_LIFETIME

.env.example

@@ -22,7 +22,6 @@ DB_PASSWORD=pixelfed
 BROADCAST_DRIVER=log
 CACHE_DRIVER=redis
 SESSION_DRIVER=redis
-SESSION_LIFETIME=120
 QUEUE_DRIVER=redis
 
 REDIS_SCHEME=tcp

.env.testing

@@ -22,7 +22,6 @@ DB_PASSWORD=
 BROADCAST_DRIVER=log
 CACHE_DRIVER=array
 SESSION_DRIVER=array
-SESSION_LIFETIME=120
 QUEUE_DRIVER=redis
 
 REDIS_SCHEME=tcp