Fix wording

Author: Lorenzo Caggioni

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

@@ -96,7 +96,7 @@ Run the samples
 
     python -m pushtotalk --device-id 'my-device-identifier' --device-model-id 'my-model-identifier' -o out.wav
 
-- Send a text request to the Assistant::
+- Send text requests to the Assistant::
 
     python -m textinput --device-id 'my-device-identifier' --device-model-id 'my-model-identifier'