[fix] OpenAI API object: completion to text_completion (NVIDIA#318)

Author: alec-flowers

lib/llm/src/protocols/openai/completions/aggregator.rs

@@ -141,7 +141,7 @@ impl DeltaAggregator {
             created: aggregator.created,
             usage: aggregator.usage,
             model: aggregator.model,
-            object: "completion".to_string(),
+            object: "text_completion".to_string(),
             system_fingerprint: aggregator.system_fingerprint,
             choices,
         })
@@ -201,7 +201,7 @@ mod tests {
                     finish_reason,
                     logprobs: None,
                 }],
-                object: "completion".to_string(),
+                object: "text_completion".to_string(),
             }),
             id: Some("test_id".to_string()),
             event: None,
@@ -310,7 +310,7 @@ mod tests {
                         logprobs: None,
                     },
                 ],
-                object: "completion".to_string(),
+                object: "text_completion".to_string(),
             }),
             id: Some("test_id".to_string()),
             event: None,