Apply suggestions from code review

Co-authored-by: Alexandre Aubin <alex.aubin@mailoo.org>

apps.json

@@ -735,7 +735,7 @@
     },
     "emailpoubelle": {
         "category": "small_utilities",
-        "level": 1,
+        "level": 6,
         "state": "working",
         "url": "https://github.com/YunoHost-Apps/emailpoubelle_ynh"
     },
@@ -1237,7 +1237,7 @@
     },
     "horde": {
         "category": "communication",
-        "level": 1,
+        "level": 6,
         "state": "working",
         "subtags": [
             "email"