Remove snapshot_ctx_repository attr from pipeline definition

This attribute will be removed with a future release of cc-utils.
Hence, it must be removed from the pipeline definition as well.
However, this will have no impact on the current functionality as
the `ocm_repository` will be used as default for both "snapshot"
and "non-snapshot" component descriptors.

.ci/pipeline_definitions

@@ -32,7 +32,7 @@ autoscaler:
     head-update:
       traits:
         component_descriptor:
-          snapshot_ctx_repository: gardener-public
+          ocm_repository: gardener-public
         draft_release: ~
     pull-request:
       traits:
@@ -49,5 +49,4 @@ autoscaler:
             internal_scp_workspace:
               channel_name: 'C0170QTBJUW' # gardener-mcm
               slack_cfg_name: 'scp_workspace'
-        component_descriptor:
-          snapshot_ctx_repository: gardener-public
+        component_descriptor: ~