Revert id change

Author: prwhelan

x-pack/plugin/inference/qa/test-service-plugin/src/main/java/org/elasticsearch/xpack/inference/mock/TestStreamingCompletionServiceExtension.java

@@ -261,7 +261,7 @@ private StreamingUnifiedChatCompletionResults.Results unifiedCompletionChunk(Str
             return new StreamingUnifiedChatCompletionResults.Results(
                 DequeUtils.of(
                     new StreamingUnifiedChatCompletionResults.ChatCompletionChunk(
-                        "chatcmpl-AarrzyuRflye7yzDF4lmVnenGmQCF",
+                        "id",
                         List.of(
                             new StreamingUnifiedChatCompletionResults.ChatCompletionChunk.Choice(
                                 new StreamingUnifiedChatCompletionResults.ChatCompletionChunk.Choice.Delta(delta, null, null, null),