Update model to return correct model for CHAT_COMPLETION task type

Author: jaybcee

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/elastic/ElasticInferenceService.java

@@ -251,7 +251,7 @@ private static ElasticInferenceServiceModel createModel(
                 eisServiceComponents,
                 context
             );
-            case COMPLETION -> new ElasticInferenceServiceCompletionModel(
+            case CHAT_COMPLETION -> new ElasticInferenceServiceCompletionModel(
                 inferenceEntityId,
                 taskType,
                 NAME,