Add required feature for whisper example in Readme (#2539)

candle-examples/examples/whisper/README.md

@@ -12,7 +12,7 @@ file](https://huggingface.co/datasets/Narsil/candle-examples/resolve/main/sample
 from the hub.
 
 ```bash
- cargo run --example whisper --release
+ cargo run --example whisper --release --features="symphonia"
 
 > No audio file submitted: Downloading https://huggingface.co/datasets/Narsil/candle_demo/blob/main/samples_jfk.wav
 > loaded wav data: Header { audio_format: 1, channel_count: 1, sampling_rate: 16000, bytes_per_second: 32000, bytes_per_sample: 2, bits_per_sample: 16 }