refactor(model-server): drop the light-model-server OpenAPI spec

This spec was not used at all and also has no real use. WebSockets
cannot be formalized with OpenAPI.

Author: languitar

model-server-openapi/specifications/model-server-light.yaml

@@ -232,7 +232,6 @@ val openAPIgenerationPath = "${project.layout.buildDirectory.get()}/generated/op
 val openApiFiles = listOf(
     "public" to "model-server",
     "operative" to "model-server-operative",
-    "light" to "model-server-light",
     "deprecated" to "model-server-deprecated",
 )