stop using the spreadsheet for the ganeti cluster

The rationale here is that Ganeti has its own inventory and capacity
evaluation system, so we do not *need* the Spreadsheet for that
purpose. We still do need the spreadsheet for cost tracking however,
so keep the documentation procedure for machines that "are not in
Ganeti", basically.

howto/new-machine.md

@@ -93,10 +93,10 @@ taken by the installer:
 
 All commands to be run as root unless otherwise noted.
 
- 1. allocate and document the machine in the [Nextcloud
-    spreadsheet](https://nc.torproject.net/apps/onlyoffice/5395), and the [services page](https://gitlab.torproject.org/legacy/trac/-/wikis/org/operations/services), if it's a new
-    service (TODO: replace with Puppet-based inventory system, see
-    [ticket #29816](https://bugs.torproject.org/29816))
+ 1. if the machine is not inside a [ganeti](ganeti) cluster (which has its
+    own inventory), allocate and document the machine in the
+    [Nextcloud spreadsheet](https://nc.torproject.net/apps/onlyoffice/5395), and the [services page](https://gitlab.torproject.org/legacy/trac/-/wikis/org/operations/services), if it's a
+    new service
 
  2. clone the `tsa-misc` git repository on the machine:
  

howto/retire-a-host.md

@@ -77,8 +77,9 @@ provided you follow the warnings.
         echo rm -rf /srv/backups/bacula/$host.torproject.org.OLD/ | at now + 30 days
 
  14. remove from the machine from this wiki (if present in
-     documentation), the [Nextcloud spreadsheet](https://nc.torproject.net/apps/onlyoffice/5395), and, if it's an
-     entire service, the [services page](https://gitlab.torproject.org/legacy/trac/-/wikis/org/operations/services)
+     documentation), the [Nextcloud spreadsheet](https://nc.torproject.net/apps/onlyoffice/5395) (if it is not in
+     [ganeti](ganeti)), and, if it's an entire service, the [services
+     page](https://gitlab.torproject.org/legacy/trac/-/wikis/org/operations/services)
  15. if it's a physical machine or a virtual host we don't control,
      schedule removal from racks or hosts with upstream
 
@@ -216,8 +217,9 @@ of an emergency:
  8. remove from DNSwl
 
  9. remove from the machine from this wiki (if present in
-     documentation), the [Nextcloud spreadsheet](https://nc.torproject.net/apps/onlyoffice/5395), and, if it's an
-     entire service, the [services page](https://gitlab.torproject.org/legacy/trac/-/wikis/org/operations/services)
+     documentation), the [Nextcloud spreadsheet](https://nc.torproject.net/apps/onlyoffice/5395) (if it is not in
+     [ganeti](ganeti)), and, if it's an entire service, the [services
+     page](https://gitlab.torproject.org/legacy/trac/-/wikis/org/operations/services)
  10. if it's a physical machine or a virtual host we don't control,
      schedule removal from racks or hosts with upstream