Swagger: Rename Spec to Preferences (#78226)

The definition for preferences is globally named `Spec` because that's the type that cue outputs
This adds a swagger annotation to rename the definition in the swagger schema to `Preferences`
This will be easier to use in generated clients

kinds/preferences/preferences_kind.cue

@@ -8,6 +8,8 @@ description: "The user or team frontend preferences"
 lineage: schemas: [{
 	version: [0, 0]
 	schema: {
+		// Spec defines user, team or org Grafana preferences
+		// swagger:model Preferences
 		spec: {
 			// UID for the home dashboard
 			homeDashboardUID?: string