Update app.json

Author: shahsad-kp

app.json

@@ -36,7 +36,7 @@
     },
     "START_MESSAGE": {
       "description": "Optional: start message of bot, use HTML parsemode format",
-      "value": "Hello {firstname}\n\nI can store private files in Specified Channel and other users can access it from special link."
+      "value": "Hello {first}\n\nI can store private files in Specified Channel and other users can access it from special link."
     },
     "ADMINS": {
       "description": "A space separated list of user_ids of Admins, they can only create links",