docs: Update Gitea Service index.md

[IslamHeggy]

Describe the bug
I tried integrating Authentik with Gitea, so I used the configuration provided on Authentik's website and I got Gitea configuration pod failing to run, Thus Gitea server failed to start

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Gitea Service'
2. Try to replicate the setup on your system using the Helm Chart configuration
3. Check Gitea logs and you will find the error

Expected behavior
Gitea should be up and running with Authentik integration

Screenshots

Logs

Incorrect Usage: flag provided but not defined: -auto-discovery-url                                                                                                                                      

Version and Deployment (please complete the following information):