Revert gokapi headless-env change: Gokapi (v1.9.6/v2.0.1) has no GOKAPI_USERNAME/PASSWORD env

Verified against Gokapi docs + the v1.9.6 binary: no env-var headless admin setup exists in any
version. Non-interactive setup requires a pre-seeded config.json + --deployment-password. Reverting
the non-functional env so the template isn't misleading; choosing a real fix path with the user.

templates/gokapi/.felhom.yml

@@ -32,13 +32,6 @@ deploy_fields:
     locked_after_deploy: true
     description: "Az alkalmazás aldomainje"
 
-  - env_var: GOKAPI_PASSWORD
-    label: "Admin jelszó"
-    type: password
-    generate: "password:24"
-    locked_after_deploy: true
-    description: "A Gokapi admin felhasználó (admin) jelszava — ezzel tudsz belépni a kezelőfelületre"
-
 # --- App info (info page content) ---
 app_info:
   tagline: "Ideiglenes fájlmegosztás lejáró linkekkel"