fix(helm): Removing deprecated admin_api_directory to avoid config crash

[sebastianplawner]

What this PR does / why we need it:
Prevents Loki from failing to start due to a deprecated admin_api_directory field in the Helm chart values. In recent Loki versions (≥3.5.x), this field is no longer recognized, causing a parsing error. This PR deletes the field to avoid breaking existing deployments relying on legacy configurations.

Which issue(s) this PR fixes:
Fixes #18729

Special notes for your reviewer:

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
• 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

[CLAassistant]

All committers have signed the CLA.

[Jayclifford345]

Hey @sebastianplawner huge thank you for the quick fix. Would you mind running

make helm-docs

and pushing newly generated documentation that will clear up the workflow error

[sebastianplawner]

Hi @Jayclifford345, no problem at all. Thanks for reviewing my PR.

[Jayclifford345]

Okay, running workflows again and then hopefull we can get this merged

[jkroepke]

@sebastianplawner thanks for providing a quick fix!