cistech-tunnel: remove entrypoint from docker-compose.json

Runtipi's compose generator doesn't translate the entrypoint field.
The entrypoint is instead set via user-config override.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/cistech-tunnel/docker-compose.json

@@ -4,7 +4,6 @@
     {
       "name": "cistech-tunnel",
       "image": "git.alexzaw.dev/alexz/openconnect-vpn:latest",
-      "entrypoint": "/shared/entrypoint.sh",
       "environment": [
         {
           "key": "VPN_EMAIL",