message: Enable use of azure openapi api validator with --v3
diff: The Azure and Model validators
  -``` yaml $(azure-validator)
  -# default the v2 generator to using the last stable @microsoft.azure/autorest-core
  +``` yaml $(azure-validator) && !$(v3)
  +# default the v2 validator to using the last stable @microsoft.azure/autorest-core
  version: ~2.0.4413
  use-extension:
  - "@microsoft.azure/classic-openapi-validator": "~1.0.9"
  - "@microsoft.azure/openapi-validator": "~1.0.2"
  + "@microsoft.azure/classic-openapi-validator": "~1.1.5"
  + "@microsoft.azure/openapi-validator": "~1.7.0"
  +```
  +
  +``` yaml $(azure-validator) && $(v3)
  +# the v3 validator to using the last stable @microsoft.azure/autorest-core
  +version: ~3.0.5537
  +use-extension:
  + "@microsoft.azure/openapi-validator": "^1.7.0"
  ```
  ``` yaml $(model-validator)
  