fix: gitea oauth configuration

[ferruhcihan]

Description:

This PR removes Gitea oauth configuration from the gitea.gotmpl file. Gitea oauth configuration will be done by apl-gitea-operator.
Is paired with: linode/apl-tasks#108

Checklist

• Architecture Design Records have been added as adr/*.md and appended to list in adr/_index.md, if applicable.
• The values-schema.yaml file and test/** fixtures have been updated to reflect code changes, if applicable.
• The OpenApi Schema from redkubes/otomi-api project is compatible with definitions from values-schema.yaml file, if applicable.
• Helm releases are meeting otomi's baseline security policies, if applicable.
• Helm chart and helmfile changes are tested against upgrade scenario, if applicable.