Docs: Mixin runbook URLs use outdated path

[SennaSemakula]

Is your documentation request related to a feature? If so, which one?

Mimir mixin alerts

What is the solution that you would like or the expected outcome?

1. Fix runbook URL path
2. Fix broken anchor links that don't exist on the runbook page

What did you think would happen?

Clicking a runbook URL would take me directly to the relevant section. Instead, some anchors return to the top of the page.

What was your environment?

Mimir 3.0.0

Any additional context to share?

Example: https://github.com/grafana/mimir/blob/main/operations/mimir-mixin-compiled/alerts.yaml#L1269

• runbook_url: https://grafana.com/docs/mimir/latest/operators-guide/mimir-runbooks/#mimiringesternotshippingblocks