[Bugfix] Fix audio.format parameter silently ignored in chat completions (#4718)

Signed-off-by: Ricardo Noriega De Soto <rnoriega@redhat.com>

docs/serving/speech_api.md

@@ -109,7 +109,7 @@ Content-Type: application/json
 | `input` | string | **required** | The text to synthesize into speech |
 | `model` | string | server's model | Model to use (optional, should match server if specified) |
 | `voice` | string | "vivian" | Speaker name (e.g., vivian, ryan, aiden) |
-| `response_format` | string | "wav" | Audio format: wav, mp3, flac, pcm, aac, opus |
+| `response_format` | string | "wav" | Audio format: wav, mp3, flac, pcm, opus |
 | `speed` | float | 1.0 | Playback speed (0.25-4.0) |
 
 #### vLLM-Omni Extension Parameters