message: Update generating-a-client.md
  Change "petstore.json" to "petstore.yaml" in the intro text, because the code example below the text reference the "petstore.yaml" file.
diff: # <img align="center" src="./images/logo.png"> Sample : Generating a client using AutoRest
  -First, download the petstore.json example file:
  +First, download the petstore.yaml example file:
  | Platform | Command |
  |----|---|
  