message: update configuration so that --python can load v2, except when it's loading v3
diff: @@ -4,13 +4,13 @@ The V2 version of the Python Generator.
  -``` yaml $(v2-python) && $(preview)
  +``` yaml $(python) && $(preview) && !isRequested('@autorest/java')
  use-extension:
  "@microsoft.azure/autorest.python": "preview"
  try-require: ./readme.python.md
  ```
  -``` yaml $(v2-python)
  +``` yaml $(python) && !isRequested('@autorest/java')
  use-extension:
  "@microsoft.azure/autorest.python": "~3.0.56"
  try-require: ./readme.python.md
  