chore: use docker.gitea.com registry URLs (#814)

Due to ratelimits

Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/814
Reviewed-by: pat-s <pat-s@noreply.gitea.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.com>
Co-committed-by: techknowlogick <techknowlogick@gitea.com>

unittests/helm/init/init_directory_structure.sh-rootless.yaml

@@ -65,7 +65,7 @@ tests:
   - it: it does not chown /data even when image.fullOverride is set
     template: templates/gitea/init.yaml
     set:
-      image.fullOverride: gitea/gitea:1.20.5
+      image.fullOverride: docker.gitea.com/gitea:1.20.5
     asserts:
       - equal:
           path: stringData["init_directory_structure.sh"]