ci: use GH app for helm workflows

[trevorwhitney]

What this PR does / why we need it:

Change helm workflows to use GH App for auth.

Which issue(s) this PR fixes:
Fixes #14258

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[chaudum]

Otherwise LGTM

[Starefossen]

CI is failing with Error: Input required and not supplied: app-id ref. https://github.com/grafana/loki/actions/runs/11066924233/job/30749176890?pr=14281

[trevorwhitney]

hmm, app-id is definitely being provided and it's passing some builds so something for use to keep an eye on I guess?