Update manifest.json to require 3.8.1 min yunohost version

manifest.json

@@ -15,7 +15,7 @@
         "url": "http://www.librement-votre.fr"
     },
     "requirements": {
-        "yunohost": ">= 3.6.5"
+        "yunohost": ">= 3.8.1"
     },
     "multi_instance": false,
     "services": [