Remove network and appliance os_purpose for now.

As per today's SIG Std/Cert discussion, these terms may be too generic
to be useful. So let's instruct providers to use `custom` for now and
hope they will talk to use to request new purposes.

Signed-off-by: Kurt Garloff <[email protected]>

Author: garloff

Standards/scs-0102-v1-image-metadata.md

@@ -85,20 +85,18 @@ The following values are allowed
 | `minimal`          | A much more barebones general purpose image               |
 | `capinode`         | Node image built for cluster-API                          |
 | `gpu`              | Image with GPU drivers e.g. for HPC or AI                 |
-| `network`          | Image for a network appliance (router, loadbalancer, ...) |
-| `appliance`        | Other appliances (single-purpose solutions)               |
 | `custom`           | None of the above                                         |
 
-Note that no other values are currently allowed and `custom` (or `appliance`) should be used in case
+Note that no other values are currently allowed and `custom` should be used in case
 of doubt. Talk to the SCS standardization bodies if you'd like to see this list extended which is
 likely the case if you fall back to `custom`.
 
 The usage of standardized `os_distro`, `os_version`, `architecture`, and `os_purpose` help cloud users to create
 automation that works across clouds without requiring image names to be standardized. Only
 one visible public image with `os_purpose` = `generic` and the same settings for `os_distro`,
 `os_version` and `architecture` should be active on any given cloud.
-The link to the OpenStack specs and the recommended `os_purpose` was added in 7/2025 to this
-standard; a new version of the standard that requires `os_purpose` will be created later.
+The link to the OpenStack specs and the recommended `os_purpose` was added to version 1.1 of
+this standard; a new version 2 of the standard that requires `os_purpose` will be created later.
 
 The following further properties are recommended (if the features are supported):