fix: helmDefaults.skipRefresh ignored in runHelmDepBuilds (#2269)
`runHelmDepBuilds()` only checked the CLI flag (`opts.SkipRefresh`) when
deciding whether to run `helm repo update` before building dependencies.
This meant that setting `helmDefaults.skipRefresh: true` in helmfile.yaml
had no effect on the repo update call inside dep builds.
Add `!st.HelmDefaults.SkipRefresh` to the guard condition so that
`helmDefaults.skipRefresh: true` is respected alongside the CLI flag.
Signed-off-by: Aditya Menon <amenon@canarytechnologies.com>