Add information to the audio-classification examples README about --ddp_find_unused_parameters parameter (huggingface#941)

Signed-off-by: Alberto Villarreal <alberto.villarreal@intel.com>

Author: Alberto-Villarreal

examples/audio-classification/README.md

@@ -95,6 +95,8 @@ On 8 HPUs, this script should run in ~12 minutes and yield an accuracy of **80.4
 
 > If your model classification head dimensions do not fit the number of labels in the dataset, you can specify `--ignore_mismatched_sizes` to adapt it.
 
+> If you get an error reporting unused parameters in the model, you can specify `--ddp_find_unused_parameters True`. Using this parameter might affect the training speed.
+
 
 ## DeepSpeed