Upgrade to SonarQube Server 2025 Release 6.1

https://community.sonarsource.com/t/sonarqube-server-2025-release-6-1/

Explicit reminder, as part of this upgrade, also upgrade the plugins (specific FindBugs)

Also see [Deprecations and removals](https://docs.sonarsource.com/sonarqube-server/server-update-and-maintenance/release-notes#id-2026.1-2)
