www/grafana: Update 12.1.0 => 12.2.0

Release notes:
https://grafana.com/blog/2025/09/25/grafana-12-2-release-all-the-latest-features/

What's new:
https://grafana.com/docs/grafana/latest/whatsnew/whats-new-in-v12-2/

Changelogs:
https://github.com/grafana/grafana/releases/tag/v12.1.1
https://github.com/grafana/grafana/releases/tag/v12.1.2
https://github.com/grafana/grafana/releases/tag/v12.2.0

Fix build with non-default user/group.

PR: 289851