[stable-10] Announce deprecation of proxmox content (#10109)

* Announce deprecation of proxmox content.

* community.proxmox 1.0.0 likely won't be ready for the next Ansible 11 release, so adjust wording.

Author: felixfontein

changelogs/fragments/proxmox-deprecation.yml

@@ -0,0 +1,6 @@
+deprecated_features:
+  - "The proxmox content (modules and plugins) is being moved to the `new collection community.proxmox <https://github.com/ansible-collections/community.proxmox>`__.
+     In community.general 11.0.0, these modules and plugins will be replaced by deprecated redirections to community.proxmox.
+     You need to explicitly install community.proxmox, for example with ``ansible-galaxy collection install community.proxmox``.
+     We suggest to update your roles and playbooks to use the new FQCNs as soon as possible to avoid getting deprecation messages
+     (https://github.com/ansible-collections/community.general/pull/10109)."