[Bugfix] Fix Qwen3ASR language asr tag in output (#33410)

Signed-off-by: NickLucche <nlucches@redhat.com>

vllm/model_executor/models/interfaces.py

@@ -1145,6 +1145,22 @@ class SupportsTranscription(Protocol):
         """
         return None
 
+    @classmethod
+    def post_process_output(cls, text: str) -> str:
+        """
+        Post-process the raw model output text.
+
+        Some ASR models output structured formats (e.g., language tags,
+        special tokens) that need to be stripped before returning to the user.
+
+        Args:
+            text: Raw decoded text from the model.
+
+        Returns:
+            Cleaned transcription text.
+        """
+        return text
+
 
 @overload
 def supports_transcription(