Adds device_model_id flag to library README

Bug: 71593532
Change-Id: I574ed33ccc25e743dfba69250a4c28f460737ad7

Author: Fleker

google-assistant-sdk/README.rst

@@ -115,15 +115,15 @@ This reference sample implements a simple but functional client for the `Google
 
 - Run the push to talk sample. The sample records a voice query after a key press and plays back the Google Assistant's answer::
 
-    googlesamples-assistant-pushtotalk --device-id 'my-device-identifier'
+    googlesamples-assistant-pushtotalk --device-model-id 'my-device-model' --device-id 'my-device-identifier'
 
 - Try some Google Assistant voice query like "What time is it?" or "Who am I?".
 
 - Try a device action query like "Turn <nickname / model product name> on".
 
 - Run in verbose mode to see the gRPC communication with the Google Assistant API::
 
-    googlesamples-assistant-pushtotalk  --device-id 'my-device-identifier' -v
+    googlesamples-assistant-pushtotalk --device-model-id 'my-device-model' --device-id 'my-device-identifier' -v
 
 googlesamples-assistant-hotword
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -137,7 +137,7 @@ This reference sample implements a simple but functional client for the `Google
 
 - Try the hotword sample::
 
-    googlesamples-assistant-hotword
+    googlesamples-assistant-hotword --device_model_id 'my-model-identifier'
 
 For Maintainers
 ---------------

google-assistant-sdk/googlesamples/assistant/library/README.rst

@@ -56,7 +56,7 @@ Run the sample
 
 - Run the hotword sample. The sample waits for the "Ok Google" hotword, then records a voice query and plays back the Google Assistant's answer::
 
-    python -m hotword
+    python -m hotword --device_model_id 'my-model-identifier'
 
 Troubleshooting
 ---------------