[ironic] ironic-inspector bugfix branches

Hello ironicers! With the deprecation and the migration of the ironic-inspector functionalities to the new agent interface in ironic we have decided to also stop cutting bugfix branches for the project. The last bugfix branch for ironic-inspector is bugfix/12.2 supported until December 2024. We'll continue with the normal release schedule until full retirement of the project. Thanks Ciao! Riccardo