Install torchaudio as dep for examples

Summary:
This package is required in order to run emformer rnnt models, which is not a required package nor installed package for executorch yet. This diff is to add the required package.

And we are picking up the latest `torchaudio` library, which is  `2.1.0.dev20230810`

Minor notes/comments change.

Reviewed By: kimishpatel

Differential Revision: D48284923

fbshipit-source-id: aa6ef28c700cb20f7bfdbda529a609f92d1b6984

Author: guangy10

examples/install_requirements.sh

@@ -12,9 +12,13 @@
 
 # Note:
 # When getting a new version of the executorch repo (via clone, fetch, or pull),
-# you may need to re-install a new version the TorchVision nightly pip package. The
-# `TORCH_VISION_VERSION` value in this document will be the correct version for the
+# you may need to re-install a new version for all dependencies in order to the
+# models in executorch/examples/models.
+# The version in this file will be the correct version for the
 # corresponsing version of the repo.
 
 TORCH_VISION_VERSION=0.16.0.dev20230810
 pip install --force-reinstall --pre torchvision=="${TORCH_VISION_VERSION}" -i https://download.pytorch.org/whl/nightly/cpu
+
+TORCH_AUDIO_VERSION=2.1.0.dev20230810
+pip install --force-reinstall --pre torchaudio=="${TORCH_AUDIO_VERSION}" -i https://download.pytorch.org/whl/nightly/cpu