scs-0104: fix dead openstack-image-manager doc link

The implementation notes for scs-0104 pointed readers to the
openstack-image-manager documentation at
docs.scs.community/docs/iaas/components/image-manager/. The
SovereignCloudStack/docs site stopped mirroring the OSISM IaaS
component trees from osism.github.io, so that page no longer exists
and the link returns a 404.

Point it at the authoritative OSISM documentation on osism.tech, where
the Image Manager tool is now documented (verified to resolve, HTTP
200).

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Jan Klare <klare@osism.tech>

Author: jklare

Standards/scs-0104-w1-standard-images-implementation.md

@@ -57,7 +57,7 @@ Run the test script on your environment and check the error messages :)
 
 The [openstack-image-manager](https://github.com/osism/openstack-image-manager) is able to
 create all standard, mandatory SCS images for you given image definitions from a YAML file.
-Please see [its documentation](https://docs.scs.community/docs/iaas/components/image-manager/) for details.
+Please see [its documentation](https://osism.tech/docs/guides/operations-guide/openstack/tools/image-manager) for details.
 
 ## Automated tests