[backport v2.13] [SURE-9881] CA in a secret referenced in spec.helmSecretName or spec.helmSecretNameForPaths not used when pulling Fleet bundle helm chart from a git repository

[rancherbot]

This is a backport issue for #3646, automatically created via GitHub Actions workflow initiated by @p-se

Original issue body:

SURE-9881

Issue description:

The fleet documentation (https://fleet.rancher.io/ref-fleet-yaml) notes the ability to pull the chart in a bundle from a git repository:

 # Git repositories can be downloaded via unauthenticated http, by using for
  # example:
  #
  # `git::http://github.com/rancher/fleet-examples/single-cluster/helm`.

However, this git method does not use any CA configured in a secret referenced on the GitRepo spec.helmSecretName or spec.helmSecretNameForPaths. By comparison, such a CA is used when pulling the chart with simple GET of chart .tgz URL

Business impact:

Customer is unable to deploy charts via Fleet that are hosted in their internal gitea instance, which is deployed with a private CA